Database Develop

Install OOS Open Beta 8 (N) / 7 (MM) without Breaking official TWRP

This guide allows you to install OOS Open Beta 8 (N) / 7 (MM) without having to switch to modified TWRP
All credits to the respective developers
Downloads : G-Drive | MEGA
Unified Links above contains the following.
[Added] OOS Leaked Open Beta 9 (Mirror only) will modify Once it is released
1- Modded OOS Open Beta 8 (No F2FS , Downgradable to any OOS version)
2- Modded OOS Open Beta 7
3 - Debloater / Pixel Laucher (Black) and H2OS Icon Packs , Google Assistant (Unified Flashable Zip)
4- Super SU 2.78-SR5
5- Official TWRP
6 - Modified TWRP Recovery 3.0.2-1.28 Credits @eng.stk
7- Latest Xposed Installer (Beta 7 Only) (It will give you the option to download / install the latest version of framework automatically)
8- Open Beta 8 Full flash able (F2FS support with Modified Recovery @Funk Wizard)
Instructions for Clean / Dirty Flash (Over any Open Beta after 3.5.1) :
1. Boot into TWRP (modified or official which ever you are on)
2. Wipe Dalvik / ART cache & cache OR Factory Reset ( If you are coming from another ROM)
3. Flash Modded OOS Open Beta 8 (Dont Switch /system and /data to F2FS if you want to root) or Beta 7
4. Wipe Dalvik and Cache
5 . Flash official twrp as image (even if you are already on it)
6. Reboot to into recovery directly (this will prevent recovery from being overwrite by the stock)
7. Flash SuperSu (Optional)
8. Flash Debloater / Pixel Laucher (Black) and H2OS Icon Packs , Google Assistant (Clear Google App Data after Booting) (Unified Flashable Zip) (Optional)
9. Reboot to System (It will reboot twice if you flashed SuperSU) - That is normal
You are good to go :good:
Regards ,
Muhammad A. Iftikhar

Is there any kernel for this build ???

Normas Interruptor said:
Is there any kernel for this build ???
Click to expand...
Click to collapse
Eng.stk yesterday teased us with an upcoming kernel for 3.5.4 Community Beta.
Whatch this thread: http://forum.xda-developers.com/oneplus-3/development/kernel-t3404970 .

Can I dirty flash it from FreedomOS based on 3.2.7?

xGOGI said:
Can I dirty flash it from FreedomOS based on 3.2.7?
Click to expand...
Click to collapse
Nope, they are two different ROMs on different channels: for instance you could have dirty flashed if you were on 3.5.2 or 3.5.3.

I need to wipe system too? Or only cache/dalvik + data?

xGOGI said:
Can I dirty flash it from FreedomOS based on 3.2.7?
Click to expand...
Click to collapse
Yes you can as you have firmware of 3.2.7

xGOGI said:
I need to wipe system too? Or only cache/dalvik + data?
Click to expand...
Click to collapse
System Wipe only if you are coming from another ROM , I.E CM or AOSP based / Nougut

How do i flash official twrp in modified twrp, do i have to extract the downloaded file?

puschkin said:
How do i flash official twrp in modified twrp, do i have to extract the downloaded file?
Click to expand...
Click to collapse
Click Install > "Install Image" it will showup in the location you download the file should have ".img" extention .
simply download it in the phone from the link in OP.

ahmediftikhar said:
Click Install > "Install Image" it will showup in the location you download the file should have ".img" extention .
simply download it in the phone from the link in OP.
Click to expand...
Click to collapse
Thanks for the quick reply!!

puschkin said:
Thanks for the quick reply!!
Click to expand...
Click to collapse
This will further help you out

Thanks for this great tutorial, worked like a charm

I want to try new CB but more likely I will be going back to official 3.2.7 I have nandroid backup ready. My question is, if I follow your guide and then I want to restore my backup, will I be able to do it without the hassle?
Wysłane ze zmywarki

ralph78 said:
I want to try new CB but more likely I will be going back to official 3.2.7 I have nandroid backup ready. My question is, if I follow your guide and then I want to restore my backup, will I be able to do it without the hassle?
Wysłane ze zmywarki
Click to expand...
Click to collapse
You can even dirty flash this over 3.2.7 (will take some time after 1st boot to optimize apps depending on the number of apps installed) , Nandroid can be restored with out hassle if you choose to clean flash 3.2.7 after testing CB

I'm on TWRP 3.0.2-1, and I can't install Rom zip, it always tells me that zip file is corrupted. I've downloaded it twice however, once from Google drive, once from AFH.
Any idea of what's wrong?

XS_31 said:
I'm on TWRP 3.0.2-1, and I can't install Rom zip, it always tells me that zip file is corrupted. I've downloaded it twice however, once from Google drive, once from AFH.
Any idea of what's wrong?
Click to expand...
Click to collapse
Try re-flashing Twrp by downloading a fresh copy , and manually mount system before flashing the ROM ,
You can also try downloading it directly to your gdrive and let it sync in your PC / phone by "make available offline" feature in drive app

how to back from 3.5.4 to stock again?

File corrupt from both links, also.

ritchiedrama said:
File corrupt from both links, also.
Click to expand...
Click to collapse
Yes... File is corrupted... So much of mobile data wasted..

[GUIDE] [HOW TO]Flash GSIs on Pie Vendor [X01AD]

Since the Pie update GSIs are not working because of System-as-root partiton But ASUS launched a new update in which GSIs are working.
READ WHOLE THREAD CAREFULLY.
REQUIREMENTS:
Unlocked bootloader (After Unlocking bootloader you will get a Red END OF STATE Warning. Don't Worry Press Power Button on that screen
Decrypted Data
Should be on latest firmware
If You're Using PitchBlack Recovery:
1. Boot into Recovery
2. Click On Advanced > Additional > Special > Setting OTA
3. Uncheck "Disable DM-Verity" Option Here
4. Done, Now You Can Use PitchBlack To Flash GSI on Pie Vendor.
INSTALLATION METHOD:
1. Download Any GSI of A/B type.
2. Download latest magisk manager zip
3. Patch your boot.img with Magisk (Tick on Preserve dm-verity by clicking on Advanced settins in magisk) or Download from Here
4. Boot into Recovery and Wipe Data, Dalvik Cache. Do not wipe system
5. Flash patched boot.img
Note: If your data is Encrypted then This step should be done with pitchblack otherwise your data may remain encrypted
6. Flash GSI image
7. Flash latest Magisk.
8. Go to Wipe option > Select Advanced Wipe > Tick on system > Click on Repair or Resize > Click on Resize.
9. Optional : Flash Gapps According to your choice If Gapps are not included in GSI.
10. Reboot System.
There is a possibility That your device will reboot again after asus logo. Don't worry
HIT THANKS IF I HELPED YOU:good:

do you see the red state warning after booting into gsi

sir iam unable to flash gapps after flashing the gsi. TWRP says the gapps variant is incompatible. I tried to flash arm 64 pico for pie. The gsi though boots. I flashed RR pie gsi (A/B) with pie vendor.. Please help Thanks in advance

jeno33 said:
sir iam unable to flash gapps after flashing the gsi. TWRP says the gapps variant is incompatible. I tried to flash arm 64 pico for pie. The gsi though boots. I flashed RR pie gsi (A/B) with pie vendor.. Please help Thanks in advance
Click to expand...
Click to collapse
Sorry I didn't mentioned in guide, that you've to modify script of gapps to get it working. I'll upload modified gapps tomorrow. Again I apologize

jeno33 said:
do you see the red state warning after booting into gsi
Click to expand...
Click to collapse
Red state warning is due to unlocked bootloader. It'll remain as long as bootloader is unlocked. But that doesn't create any problem except for increasing boot time by 5-6 seconds.

use A/B type cannot flash gapps,error 64. A type can flash gapps. Why?

gxfuzion92 said:
use A/B type cannot flash gapps,error 64. A type can flash gapps. Why?
Click to expand...
Click to collapse
Updater-script needs to be modified inside gapps, because gapps wrongly detects architecture as arm.
Install this gappshttps://drive.google.com/file/d/1nS2z4emxHovZ0x3CqXl59r8oBqx9DiPU/view?usp=drivesdk
I have modified the script

what rums for example are loaded and working?
currently the Havoc-OS-v2.0-20181027-GSI-ARM64-Aonly-Official is being loaded and running.
tried miui, flyme, Havoc-OS other versions

Is there any video tutorial?

Any tutorial videos?

gxfuzion92 said:
use A/B type cannot flash gapps,error 64. A type can flash gapps. Why?
Click to expand...
Click to collapse
Hey you able to flash any GSI except havoc 2.0 ??

I'm not able to access your document

Install GSI on S9 Exynos

Guys I successfully installed HAVOC-OS located https://forum.xda-developers.com/project-treble/trebleenabled-device-development/gsi-havoc-os-t3930030. The steps I followed are mentioned below
1. Wipe everything except internal storage.
2. Flashed BRK3 Vendor https://mega.nz/#F!wFFQUYbI!GZvNOBSn1wVn8U9mQDzBiw!IQsjlYzA
2. Installed Endurance GSI kernel https://forum.xda-developers.com/galaxy-s9/samsung-galaxy-s9--s9-cross-device-development/kernel-endurance-kernel-v1-0-t3849434
3. Flashed the system image for ARM 64 A only
4. Boot system
5. Reboot to recovery and Flashed Mgisk
6. Gapps will fail to install at first. Just goto wipe -> Adv wipe -> system partition -> Resize. Reboot to recovery and flash Gapps
7. Reboot and enjoy
8. You can test other GSI Roms also and report. The thread is located at https://forum.xda-developers.com/project-treble/trebleenabled-device-development

Thanks buddy. I was looking for the ways to run the GSI. And the method works. Good job

thanks for the guide! im still on an unrooted s9, but if everything works ill definetly make the jump. Can you tell us more about stability, bugs and if there are things not working

So after testing the ROM for 2 days I can say that
1. It is very stable and can be used as a daily driver
2. Everything works, I am not sure about Bluetooth audio though, haven't checked it
3. It can be heavily customized. Unlike LOS, where we have only few of these features available
4. Battery life is the best I got using any other ROM out there (check the screens below). and I am the guy who gets 3 hrs of SOT, when others claimed 5+ hrs on the same ROM.
5. Security patch is latest even as compared to the TW ROMs
6. Regarding camera... Its the same as LOS pie. Use gcam by idan 3.5 fixed and you are good to go.

fingerprint working?

andreMusers said:
fingerprint working?
Click to expand...
Click to collapse
Yes it is

Thanks for trying this out. I'm only a few months in with my exynos S9 on android pie, so I haven't yet learned the details about rooting/recovery for this phone.
I'll wait for your next update regarding daily use, and would love a more detailed step-by-step for installation if that's not too much trouble. I'm honestly loving those screenshots.

How about IMEI, BRK3 Vendor safe..?

Ok here is the detailed tutorial on how to install a GSI rom
1. First you need to wipe everything in TWRP. Just like you do, when you clean flash any rom
2. Than install the BRK3 vendor. Link is provided by the OP. It's a flashable zip file so just flash it like any other zip.
3. Flash the Endurance GSI kernel. Link is in the OP.
4. Next, download the GSI rom from the link in the OP. Remember to download the ARM 64 A-only variant.
5. Extract the files and you should get a . Img file. Copy that in the SD card
6. In the TWRP, goto install. Select flash image from the bottom right corner of your screen. Now browse the image file, that you copied and choose system image and install.
7. Boot to the system and than boot back to the recovery.
8. Now flash the magisk
9. If you try to install gapps, it will give an error regarding space. So just goto wipe -> advance wipe > system repartition > resize
After resize, you will be able to install gapps.
Flash gapps, automatic brightness fix ( link in the rom thread), AOD fix ( link in the rom thread) and reboot.

burninitup said:
Ok here is the detailed tutorial on how to install a GSI rom
1. First you need to wipe everything in TWRP. Just like you do, when you clean flash any rom
2. Than install the BRK3 vendor. Link is provided by the OP. It's a flashable zip file so just flash it like any other zip.
3. Flash the Endurance GSI kernel. Link is in the OP.
4. Next, download the GSI rom from the link in the OP. Remember to download the ARM 64 A-only variant.
5. Extract the files and you should get a . Img file. Copy that in the SD card
6. In the TWRP, goto install. Select flash image from the bottom right corner of your screen. Now browse the image file, that you copied and choose system image and install.
7. Boot to the system and than boot back to the recovery.
8. Now flash the magisk
9. If you try to install gapps, it will give an error regarding space. So just goto wipe -> advance wipe > system repartition > resize
After resize, you will be able to install gapps.
Flash gapps, automatic brightness fix ( link in the rom thread), AOD fix ( link in the rom thread) and reboot.
Click to expand...
Click to collapse
Thanks for the extra instruction man, will test this out soon.

burninitup said:
Ok here is the detailed tutorial on how to install a GSI rom
1. First you need to wipe everything in TWRP. Just like you do, when you clean flash any rom
2. Than install the BRK3 vendor. Link is provided by the OP. It's a flashable zip file so just flash it like any other zip.
3. Flash the Endurance GSI kernel. Link is in the OP.
4. Next, download the GSI rom from the link in the OP. Remember to download the ARM 64 A-only variant.
5. Extract the files and you should get a . Img file. Copy that in the SD card
6. In the TWRP, goto install. Select flash image from the bottom right corner of your screen. Now browse the image file, that you copied and choose system image and install.
7. Boot to the system and than boot back to the recovery.
8. Now flash the magisk
9. If you try to install gapps, it will give an error regarding space. So just goto wipe -> advance wipe > system repartition > resize
After resize, you will be able to install gapps.
Flash gapps, automatic brightness fix ( link in the rom thread), AOD fix ( link in the rom thread) and reboot.
Click to expand...
Click to collapse
Doesn't work. Stuck on boot logo, loading forever.

Zwulf said:
Doesn't work. Stuck on boot logo, loading forever.
Click to expand...
Click to collapse
me too dont know any fix
EDIT: Somehow i managed to boot the rom but sim won't get detected

Double tap and AOD - work correctly? On snap it does not work well

My Baseband version is now unknown
I have an SM-G960F and its german
EDIT:I just flashed the latest firmware from soldier and now sim card gets detected

Masterofchicken said:
My Baseband version is now unknown
I have an SM-G960F and its german
EDIT:I just flashed the latest firmware from soldier and now sim card gets detected
Click to expand...
Click to collapse
So camera isn't working ,root is still present with magisk and i couldn't disable it with the adb command so safetynet doesn't pass ,i'll say it's not really usable ?

Has anyone found a fix for getting stuck at the s9 logo?..wanting to move to GSI ROMs

I have tried this,
After flash GSI rom, reboot recovery, reboot system and I have bootloop with the first logo Galaxy S9. Can anybody please help me?

@arunrawat2112
Finally I was able to flash some roms but none of them work properly. Can you please help me?

[GUIDE] ROM flashing the easy way

We all know flashing ROMs got a lot more complicated with the advent of A/B partitions.
This is not my work, the aim here is only to highlight a process which simplifies the task.
Original post on the OnePlus 6 forum can be found here:
https://forum.xda-developers.com/oneplus-6/how-to/script-copy-oxygenos-base-partitions-to-t4097979
It makes use of a script which copies the flashed firmware to both slots without having to reboot recovery and do it a second time. Also by not having to reboot recovery you avoid the issue where internal storage becomes unreadable.
Credit for this goes to:
LineageOS @erfanoabdi @filipepferraz @Prakyy @drpradsms
Download by prakky (hit the thanks button on his post below):
https://androidfilehost.com/?fid=8889791610682890605
The following posts detail it's usage which you follow at your own risk.

Clean Flashing a new ROM
Disable lockscreen security
Boot TWRP 3.4+
1) Flash latest OOS
2) Flash ROM
3) Flash TWRP installer
4) Flash Finalize.zip
5) Format data; type 'yes' (backup as this wipes phone)
6) Boot System
Reboot recovery to flash additional zips.

Updating OOS base whilst on a custom ROM
Boot TWRP 3.4+
1) Flash latest OOS
2) Flash ROM
3) Flash TWRP installer
4) Flash Finalize.zip
5) Boot System
Reboot recovery to flash additional zips.

Updating a custom ROM (nothing fancy here)
Boot TWRP 3.4+
1) Flash ROM
2) Flash TWRP installer
3) Boot System
Reboot recovery to flash additional zips.

Reverting to OOS
WARNING I've yet to test this!
Boot TWRP 3.4+
1) Flash latest OOS
2) Flash Finalize.zip
3) Format data; type 'yes' (backup as this wipes phone)
4) Boot System
Note: this will revert you to stock recovery as well.

Tip:
Chain install the zips by selecting 'Add more Zips' after selecting the first zip.
Only 'Swipe to confirm Flash' once all zips have been queued.
I recommend numbering the zips in the order they need flashed.

Note: this issue is now resolved as of 09/08/20 as per https://forum.xda-developers.com/oneplus-6t/how-to/guide-rom-flashing-easy-t4143701/post83241857
As a side note and given that I show an OmniROM zip in the previous screenshots here's a fix required for flashing OmniROM.
I use Mixplorer to do the following.
1) Open the OmniROM weekly zip
2) Navigate to folder shown
3) Open metadata
4) Edit oneplus6t to OnePlus6T
5) Save metadata
OmniROM will now flash successfully in TWRP.

Nice post! Don't mean to be rude but is kinda redundant as my thread already existed: https://forum.xda-developers.com/oneplus-6/how-to/script-copy-oxygenos-base-partitions-to-t4097979

Prakyy said:
Nice post! Don't mean to be rude but is kinda redundant as my thread already existed: https://forum.xda-developers.com/oneplus-6/how-to/script-copy-oxygenos-base-partitions-to-t4097979
Click to expand...
Click to collapse
Didn't know your post existed. Only learnt about the method on Pixen OS thread which uses it and gives you credit as did I. A lot of people only look in their own phone forum. If you don't mind I'll leave this thread open. However if you aren't happy I'll ask a mod to close it.

Deleted. Think maybe I'm getting altimeters. ?

Prakyy said:
Nice post! Don't mean to be rude but is kinda redundant as my thread already existed: https://forum.xda-developers.com/oneplus-6/how-to/script-copy-oxygenos-base-partitions-to-t4097979
Click to expand...
Click to collapse
Edited first post to make it clearer this is your work.

mitchst2 said:
Didn't know your post existed. Only learnt about the method on Pixen OS thread which uses it and gives you credit as did I. A lot of people only look in their own phone forum. If you don't mind I'll leave this thread open. However if you aren't happy I'll ask a mod to close it.
Click to expand...
Click to collapse
You can keep it open ofc I don't mind.
However, yes, many people only see in their device's forums but since this script will work w/ any A/B device, is there a forum I could post in so that all device owners can see it??

Prakyy said:
You can keep it open ofc I don't mind.
However, yes, many people only see in their device's forums but since this script will work w/ any A/B device, is there a forum I could post in so that all device owners can see it??
Click to expand...
Click to collapse
Good question.
Is 'Android Development and Hacking / General' the right place? There are some all device guides with a lot of views in there.
https://forum.xda-developers.com/android/general

mitchst2 said:
As a side note and given that I show an OmniROM zip in the previous screenshots here's a fix required for flashing OmniROM.
I use Mixplorer to do the following.
1) Open the OmniROM weekly zip
2) Navigate to folder shown
3) Open metadata
4) Edit oneplus6t to OnePlus6T
5) Save metadata
OmniROM will now flash successfully in TWRP.
Click to expand...
Click to collapse
As of 09/08/20 build and this commit all is well with OMNI and TWRP again. No need to edit the ROM zip anymore.

Is there a proper way to switch from one custom rom to another without formatting the data? Encryption and A/B made the custom rom game so crazy and time taking now. Or maybe I lost track of things. I could always take a backup of storage on laptop but the backups are very huge, mostly 80gb+ and takes forever while backing up whatsapp databases with images thumbnails and all.

brajesh.sharma87 said:
Is there a proper way to switch from one custom rom to another without formatting the data? Encryption and A/B made the custom rom game so crazy and time taking now. Or maybe I lost track of things. I could always take a backup of storage on laptop but the backups are very huge, mostly 80gb+ and takes forever while backing up whatsapp databases with images thumbnails and all.
Click to expand...
Click to collapse
No when switching ROM formatting data will be necessary. Not used it myself but others recommend Migrate to restore apps and data.

I was looking for a way to backup current rom using twrp, test a rom and then be back on the original rom with a twrp restore. If anyone finds a way to do this without format data, pls let me know.

brajesh.sharma87 said:
I was looking for a way to backup current rom using twrp, test a rom and then be back on the original rom with a twrp restore. If anyone finds a way to do this without format data, pls let me know.
Click to expand...
Click to collapse
I just restored PiXeN from AOSPA on 6t device and had no issues and I did NOT format my data or do anything but let TWRP do it's restore then rebooted system.. Just backup your system, data and boot partitions and restore them then reboot system. I didn't encrypt my backup using a pw in recovery. I also use magisk canary latest and the themed TWRP recovery 3.4.0-v1 from EvoX rom that acuicultor compiles and morphine1 themes. I've not restored yet using any other TWRP so not sure what works and what doesn't as far as that goes but the themed recovery works for me.
**Formatting data is unavoidable when installing an AOSP custom rom coming from stock OOS rom.
Edit

flash713 said:
I just restored PiXeN from AOSPA on 6t device and had no issues and I did NOT format my data or do anything but let TWRP do it's restore then rebooted system.. Just backup your system, data and boot partitions and restore them then reboot system. I didn't encrypt my backup using a pw in recovery. I also use magisk canary latest and the themed TWRP recovery 3.4.0-v1 from EvoX rom that acuicultor compiles and morphine1 themes. I've not restored yet using any other TWRP so not sure what works and what doesn't as far as that goes but the themed recovery works for me.
**Formatting data is unavoidable when installing an AOSP custom rom coming from stock OOS rom.
Edit
Click to expand...
Click to collapse
I had to mandatory format data when I wanted to move from evolution x to aospa.

brajesh.sharma87 said:
I had to mandatory format data when I wanted to move from evolution x to aospa.
Click to expand...
Click to collapse
And I've also had to format data before as well but not lately. Could it be because I format both slots coming from OOS or because I use Canary Magisk or the recovery I use.. No idea but next time you are on EvoX backup system, data and boot and try and restore it using that recovery that comes with EvoX and see what happens. These last few weeks I've stayed on AOSiP and PixeN and I flashed Omni once I think but restoring from AOSPA to Pixen was flawless for me and also restoring Pixen to Pixen was also fine, which I do because I always mess around with sound mods.... I'm on AOSiP now and soon as I get more charge on my phone I'm going to try and restore to something I have a backup already made on one of my USB drives and I'll edit this post and report what the outcome is...

how downgrade sm-a605fn from android 10 to 9

Hello, I have a Samsung Galaxy A6+ with latest fw installed.
(italian version)
A605FNXXU7CUD4
The phone is totally useless after the update to android 10, it takes AGES to perform any action, even open the Camera or open a Message.
Already tried to wipe everything, hard reset, reinstall fw. Still useless.
Since I’d like to downgrade to Android 9 to have back a useful phone, I tried to install the latest Android 9 fw with Odin.
A605FNXXS5BTB1
But it fails, saying SW REV CHECK FAIL : [aboot] Fused 7 > Binary 5
What can I do?
Is there any chance to downgrade this phone?
Thank you

1. Unlock your bootloader.
2. Flash custom recovery for your device.
3. Go to custom recovery (TWRP) and flash any downloaded custom rom (for your device), GSI or save stock firmware as flashable zip with tool like ClassyKitchen.
4. Flash Magisk or RMM-bypass-v3 in TWRP to protect your bootloader from getting locked again.
Backup your personal data at first, of course.

nqnxev said:
1. Unlock your bootloader.
2. Flash custom recovery for your device.
3. Go to custom recovery (TWRP) and flash any downloaded custom rom (for your device), GSI or save stock firmware as flashable zip with tool like ClassyKitchen.
4. Flash Magisk or RMM-bypass-v3 in TWRP to protect your bootloader from getting locked again.
Backup your personal data at first, of course.
Click to expand...
Click to collapse
Almost done, but I can't find any custom rom available for download. Can someone help? Since wwith twrp I cannot install a stock rom. Thanks in advance.

I managed to flash a so called Ari's rom, but I think the phone is now bricked. It is on bootloop on the first screen of Samsung (with phone name and so on) and with SET WARRANTY BIT : KERNEL at top left. I think it is time to trash it or does someone have any hint? Thanks

Ecto1000 said:
I managed to flash a so called Ari's rom, but I think the phone is now bricked. It is on bootloop on the first screen of Samsung (with phone name and so on) and with SET WARRANTY BIT : KERNEL at top left. I think it is time to trash it or does someone have any hint? Thanks
Click to expand...
Click to collapse
I proposed three different options: custom rom, GSI (generic system image) or conversion stock firmware to flashable form. If there's no good custom rom for A6+, then don't worry - you can still try another options. Try playing with Generic System Images:
1. Flash your current stock firmware as usual in Odin.
2. Unlock bootloader and flash TWRP.
3. Go to TWRP.
4. Wipe partitions cache, dalvik, data, system (don't wipe vendor partition - it's needed).
5. Flash GSI image (recommended will be at first phhusson's AOSP (Android 9 or 10)) as "system image". You always need to choose and download "arm32_binder64" variant of img file.
6. Reboot to your new system.
Second option is to convert stock Android 9 firmware into flashable form.
1. Download ClassyKitchen tool.
2. Import downloaded Android 9 stock firmware (for your phone) into it and save it as flashable zip.
3. Go to TWRP.
4. Wipe cache, dalvik, data, system and vendor.
5. Flash your previously done zip with Android 9 as any other flashable zip in TWRP.
6. Flash Magisk or RMM-state-bypass-v3 in TWRP to prevent your bootloader from getting locked again.
7. Reboot.

I went for the second option, in Classykitchen I loaded the stock android 9 rom and selected
BUILD ZIP ROM (for recovery).
Then installed with TWRP following your wipe indications.
Success.
But when I went to install RMM-state-bypass-v3 I got the error impossile to mount /system.
So I rebooted twrp and before anything I manually mounted SYSTEM in twrp in the dedicated MOUNT menu, and I did everything again from wipe to install.
Is this procedure correct?
Success, success also for RMM-state-bypass-v3.
I rebooted but I'm again stuck in the same loop described in my previous reply.
When I selecr REBOOT in twrp, do I have to flag anything? For example System?
Regarding the first option, if I go there:
Releases · phhusson/treble_experimentations
Notes about tinkering with Android Project Treble. Contribute to phhusson/treble_experimentations development by creating an account on GitHub.
github.com
exactly which file do I have to download among ASSETS of any release?
Thank you very much

Ecto1000 said:
I went for the second option, in Classykitchen I loaded the stock android 9 rom and selected
BUILD ZIP ROM (for recovery).
Then installed with TWRP following your wipe indications.
Success.
But when I went to install RMM-state-bypass-v3 I got the error impossile to mount /system.
So I rebooted twrp and before anything I manually mounted SYSTEM in twrp in the dedicated MOUNT menu, and I did everything again from wipe to install.
Is this procedure correct?
Click to expand...
Click to collapse
Yes, it's correct. If RMM bypass or Magisk.zip was flashed without any errors in TWRP then everything is okay. Just reboot to system in TWRP after that - there is option to reboot directly to system. First boot always can take a bit longer than next boots.
Ecto1000 said:
exactly which file do I have to download among ASSETS of any release
Click to expand...
Click to collapse
You always need to get any "arm32_binder64" (always AB) image. Gapps or vanilla is just your choice. Just get Android 9 or 10 image and flash it as "system image" (but wipe at first partitions specified in my previous post - don't wipe only Vendor partition, because it contains important things). Android 12 GSI still aren't stable. Android 11 - maybe will work properly. Android 9 and 10 should work fine. There is even short article about GSI on Galaxy A6+ with some fixes for that device attached:
Samsung Galaxy A6 Plus (2018)
Notes about tinkering with Android Project Treble. Contribute to phhusson/treble_experimentations development by creating an account on GitHub.
github.com
You can try of course other GSI's as well:
Generic System Image (GSI) list
Notes about tinkering with Android Project Treble. Contribute to phhusson/treble_experimentations development by creating an account on GitHub.
github.com

Thank you very much, appreciated.
But something weird happens: I install the ROM with success. If then I try to install Magisk (or Rmm) it fails with error 7.
And twrp says No Os installed if I reboot.
But if I try to install Magisk after rebooting into twrp after installing the ROM it goes without errors.
But anyway I have the issues of No Os installed.

Ecto1000 said:
Thank you very much, appreciated.
But something weird happens: I install the ROM with success. If then I try to install Magisk (or Rmm) it fails with error 7.
And twrp says No Os installed if I reboot.
But if I try to install Magisk after rebooting into twrp after installing the ROM it goes without errors.
But anyway I have the issues of No Os installed.
Click to expand...
Click to collapse
You need to reboot to recovery after flashing new system, because just after flashing TWRP doesn't recognize it - that is why you see that "no OS installed". Just reboot your phone to recovery again (you have such option in TWRP). In case of GSI (except maybe CAOS, LineageOS Q/R mod) Magisk or RMM bypass is not needed.
Btw, in case of any problems with hardware support on GSI flash also that patch in TWRP (it may be needed to mount "Vendor" partition in TWRP before flashing that fixes):
Fixes.zip
drive.google.com

Thank you again for your help.
I already rebooted to recovery and twrp keeps saying NO OS.
I'm using twrp 3.5.2_10-0.
I'm starting to suspect that this behaviour is due to the fact that this version of twrp could be too much new and unstable for my phone.
So I'd like to install an older version of twrp with Odin, as explained here:
TWRP for SM-A605FN Samsung Galaxy A6+
How to Install TWRP 3.2.3-1 on Galaxy A6+ SM-A605FN Android 8.0.0 Oreo. Once you installed TWRP recovery on your Samsung Galaxy A6+ SM-A605FN, you can customize it, Rooting or installing custom ROM
www.recovery-mode.com
But I cannot manage to go into download mode again, even from REBOOT menu of twrp it doesn't work, I keep staying in the loop explained before.
Moreover your first option of GSI need me to go into download mode to install the latest stock ROM with Odin.
I just manage to get into the attached screen.
Any idea?
Thank you again

It's not possible to ignore that message and just flash latest stock firmware via Odin? Odin refuses flashing latest stock firmware?
Other builds of TWRP for your devices you'll find here:
Releases · roynatech2544/TWRP_device_samsung_a6plte
Contribute to roynatech2544/TWRP_device_samsung_a6plte development by creating an account on GitHub.
github.com
But don't use TWRP older than 3.4.0, because it doesn't have support for "Vendor" partition.

Yes, I managed to ignore that screen and go in download mode again.
I tried to follow your first option since the second one was not successful.
Installed latest stock and then twrp 3.5.0-1.
Wipe as you explained, I flash the Gsi
system-quack-arm32_binder64-ab-gapps.img
The flash is very fast, but no errors, is it normal?
After that I reboot to recovery in order to flash
Disable_DM-Verity_ForceEncrypt_11.02.2020
it goes but just at the end it gives the error
failed to mount /odm no such file or directory.
And if I reboot to system the phone loops as always.
I'm losing all hope...

Ecto1000 said:
system-quack-arm32_binder64-ab-gapps.img
Click to expand...
Click to collapse
It's okay, but it's possible that you'll always need "vndklite" images for working camera.
Ecto1000 said:
The flash is very fast, but no errors, is it normal?
Click to expand...
Click to collapse
If you flashed it as "System Image" and it was successful then yes - should be fine. DM-Verity isn't needed for GSI - only RMM bypass v3 is sometimes needed (on CAOS, Lineage Q/R mod and maybe in case of some other images). On usual A600FN RMM bypass is not needed on phhusson AOSP. Just format "Data" partition (format, not only wipe) - it will remove encryption for you.
Procedure of flashing should be like that:
1. Wipe: cache, dalvik, data, system ("Vendor" partition leave untouched, because it's important for GSI - that is why you needed to flash stock firmware at first, because it adds vendor files for your phone, but it's needed only once, just don't wipe "Vendor").
2. Flash your GSI as "System Image".
3. Reboot phone (to recovery again).
4. Mount your "data", "vendor" and "system" partition.
5. Flash your zips: RMM bypass v3 (optionally Magisk).
5. Reboot to your new system now.
In case of any hardware support problems, reboot to TWRP again, mount "Vendor" partition and flash that fixes:
Fixes.zip
drive.google.com
Try to boot Android 10 or Android 9 images. If it will succeed, then you can try flashing Android 11 images and check what works, and what not. According to that article

nqnxev said:
It's okay, but it's possible that you'll always need "vndklite" images for working camera.
Click to expand...
Click to collapse
I don't know what are those images. Can you explain better?
When I proceed with RMM bypass V3 I see the errors in the attached image. It seems like there is a problem in writing to /system.
Can this be related to the hardware support problems you mentioned?
I tried with different versions of Twrp already and with Havoc Os too.
Should I try with flashing a different ROM ?
Thanks again

Ecto1000 said:
I don't know what are those images. Can you explain better?
Click to expand...
Click to collapse
Just look at filename of system images. But as I see, it's apparently important on Android 11 and newer. For now, try to boot Android 10 or 9. Let's try with that image:
https://github.com/phhusson/treble_experimentations/releases/download/v222/system-quack-arm32_binder64-ab-vanilla.img.xz
1. Decompress that image.
2. Copy to SD card or to internal storage.
3. Wipe cache, dalvik, data, system.
4. Format data partition (it's needed only once).
5. Flash downloaded and extracted file as "System Image".
6. Reboot phone to recovery (again).
7. Select in TWRP: Mount -> system, data, vendor.
8. Flash RMM bypass v3 (or Magisk).
9. Reboot now to system.
10. In case of some things not working, go back to TWRP and mount vendor partition (Mount -> tick "Vendor" -> go back to flashing zips) and flash that:
Fixes.zip
drive.google.com
11. Reboot to system again and check if now everything works properly.
Ecto1000 said:
When I proceed with RMM bypass V3 I see the errors in the attached image. It seems like there is a problem in writing to /system.
Click to expand...
Click to collapse
Yes, because you need to mount that partitions in TWRP:
Mount -> tick "system", "vendor" and "data" - and now flash whatever you want.

The only "receipt" which isn't giving installation errors is following your last instructions but avoiding to reboot to recovery after ROM flash (used Vanilla), and using Magisk v22 with unticked the line called "skip digest check" . See attached images.
Anyway, still no success to get into android.
Also tried fixes.zip.

Maybe I have to try with sideload ?

Ecto1000 said:
The only "receipt" which isn't giving installation errors is following your last instructions but avoiding to reboot to recovery after ROM flash (used Vanilla), and using Magisk v22 with unticked the line called "skip digest check" . See attached images.
Anyway, still no success to get into android.
Also tried fixes.zip.
Click to expand...
Click to collapse
Everything seems to be okay in your photos. What happens when you press "Reboot System"?

nqnxev said:
Everything seems to be okay in your photos. What happens when you press "Reboot System"?
Click to expand...
Click to collapse
The phone goes into loop with the attached screen and black screen alternatively.
On the top you can see SET WARRANTY BIT: KERNEL, it should be normal right?
Do I have to set something inside MOUNT of twrp before rebooting to system?

Ecto1000 said:
The phone goes into loop with the attached screen and black screen alternatively.
On the top you can see SET WARRANTY BIT: KERNEL, it should be normal right?
Do I have to set something inside MOUNT of twrp before rebooting to system?
Click to expand...
Click to collapse
I've never had such problem, but according to that thread it seems that it's a fault of modified kernel (so don't flash Magisk with GSI, because it patches kernel).
Try to flash stock firmware, unlock bootloader, flash TWRP, format "data" partition, wipe partitions (cache, dalvik, system, data) and flash GSI image as "system image". And reboot to system.
Don't flash RMM and Magisk for now - and check if system will run properly.