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Can't root LG-H811 20p because supersu soft bricks phone

So I connected my LG-H811 running stock ROM 20p to my PC successfully and ran adb and fastboot to transfer twrp and supersu over to the phone internal drive. So far so good. I couldn't get twrp to flash properly, so I simply did a temporary boot and got twrp to run without flashing it as a recovery. Then I used twrp to flash supersu (SuperSU-v1.94.zip). The problem is that when I try to reboot, it says the superSU binary is not installed. So I tried newer versions of supersu (SuperSU-v2.76-20160630161323.zip and SuperSU-v2.48.zip). Each time with these newer versions it soft bricked the phone again and required a full stock ROM restore. Specifically, it hangs either on the black LG screen or the white T-mobile screen, while the blue LED flashes on and off every few seconds. To unbrick it each time, I did a restore with stock ROM H811V20p_00_0913.kdz with LGUP. That got it working again with stock ROM, but no root. There must be a way to get superSU to install on 20p (and even get the twrp recovery to flash). I unlocked the bootloader, and it seems to load, so apparently that's not the issue. Thanks.

theprof7 said:
So I connected my LG-H811 running stock ROM 20p to my PC successfully and ran adb and fastboot to transfer twrp and supersu over to the phone internal drive. So far so good. I couldn't get twrp to flash properly, so I simply did a temporary boot and got twrp to run without flashing it as a recovery. Then I used twrp to flash supersu (SuperSU-v1.94.zip). The problem is that when I try to reboot, it says the superSU binary is not installed. So I tried newer versions of supersu (SuperSU-v2.76-20160630161323.zip and SuperSU-v2.48.zip). Each time with these newer versions it soft bricked the phone again and required a full stock ROM restore. Specifically, it hangs either on the black LG screen or the white T-mobile screen, while the blue LED flashes on and off every few seconds. To unbrick it each time, I did a restore with stock ROM H811V20p_00_0913.kdz with LGUP. That got it working again with stock ROM, but no root. There must be a way to get superSU to install on 20p (and even get the twrp recovery to flash). I unlocked the bootloader, and it seems to load, so apparently that's not the issue. Thanks.
Click to expand...
Click to collapse
have twrp .img in sd card and install click on image tab.. then select recovery and flash it.
once it flashes i just flash superSU and get root.

raptorddd said:
have twrp .img in sd card and install click on image tab.. then select recovery and flash it.
once it flashes i just flash superSU and get root.
Click to expand...
Click to collapse
Thanks raptorddd, but that's exactly the problem. I did flash superSU using twrp, and it seemed to install fine. I expected that I would simply get root as you say, but that's not what happened. The first time with SuperSU v1.94 newly installed, the phone rebooted normally, and the superSU app showed up, but it didn't work because it said there was no binary installed. The newer versions of superSU simply soft-bricked the phone. So I need a way to get superSU to work and not soft-brick the phone. Is there a preferred version of superSU for LG-H811 ROM 20p, or some obscure setting that makes it work?

theprof7 said:
Thanks raptorddd, but that's exactly the problem. I did flash superSU using twrp, and it seemed to install fine. I expected that I would simply get root as you say, but that's not what happened. The first time with SuperSU v1.94 newly installed, the phone rebooted normally, and the superSU app showed up, but it didn't work because it said there was no binary installed. The newer versions of superSU simply soft-bricked the phone. So I need a way to get superSU to work and not soft-brick the phone. Is there a preferred version of superSU for LG-H811 ROM 20p, or some obscure setting that makes it work?
Click to expand...
Click to collapse
did you open the app and clicked on update binaries.? if it asks to.?
here mine try this. then update from PS.
https://drive.google.com/file/d/0B90RfjoH13UEbDFBSG5XWVA0ME0/view?usp=sharing

raptorddd said:
did you open the app and clicked on update binaries.? if it asks to.?
here mine try this. then update from PS.
Thanks -- that's the the exact same version of superSU I used earlier (I even ran a diff, and the files are identical). After I flashed this version of superSU on the p20 stock ROM with twrp, it soft-bricked my phone. By that I mean it got to the boot page, and the blue LED pulsed on and off every few seconds, and it never got beyond that. When I flashed superSU v1.94, at least it booted afterward, but when I opened the superSU app, it didn't even give me the option to update binaries -- it just said the binary isn't installed, and so superSU can't run, it exited.
Maybe I'll try flashing an earlier stock ROM and see if that allows superSU to flash and run properly -- not sure which ones are compatible given the anti-rollback versioning.
Click to expand...
Click to collapse

theprof7 said:
raptorddd said:
did you open the app and clicked on update binaries.? if it asks to.?
here mine try this. then update from PS.
Thanks -- that's the the exact same version of superSU I used earlier (I even ran a diff, and the files are identical). After I flashed this version of superSU on the p20 stock ROM with twrp, it soft-bricked my phone. By that I mean it got to the boot page, and the blue LED pulsed on and off every few seconds, and it never got beyond that. When I flashed superSU v1.94, at least it booted afterward, but when I opened the superSU app, it didn't even give me the option to update binaries -- it just said the binary isn't installed, and so superSU can't run, it exited.
Maybe I'll try flashing an earlier stock ROM and see if that allows superSU to flash and run properly -- not sure which ones are compatible given the anti-rollback versioning.
Click to expand...
Click to collapse
try a custom kernel it has superSU installed.. i say imperium kernel.
try first the custom kernel.. if not you can only downgrade to 20o. no lower or youll hard brick phone.
Click to expand...
Click to collapse

OK so I finally got root. The key was to copy over this file to the phone's internal memory:
Imperium_Kernel_G4_H811_v4.8a.zip
Then:
adb reboot bootloader
fastboot boot twrp-3.0.2-0-h811.img
Then in TWRP, flash the imperium kernel. After that everything worked with root, though I still can’t get the twrp recovery to flash properly. Having root is good enough for now though.
EDIT: just now got TWRP to flash using flashify, so everything works. On to unlocking...

can you please share what guide you used to unlock and root this phone? I'm having issues on finding it, im on the newest update

theprof7 said:
OK so I finally got root. The key was to copy over this file to the phone's internal memory:
Imperium_Kernel_G4_H811_v4.8a.zip
Then:
adb reboot bootloader
fastboot boot twrp-3.0.2-0-h811.img
Then in TWRP, flash the imperium kernel. After that everything worked with root, though I still can’t get the twrp recovery to flash properly. Having root is good enough for now though.
EDIT: just now got TWRP to flash using flashify, so everything works. On to unlocking...
Click to expand...
Click to collapse
Please, can you share what guide you used to unlock and root this phone (20p)? Can not find any complex info anywhere.
Thank you.

theprof7 said:
OK so I finally got root. The key was to copy over this file to the phone's internal memory:
Imperium_Kernel_G4_H811_v4.8a.zip
Then:
adb reboot bootloader
fastboot boot twrp-3.0.2-0-h811.img
Then in TWRP, flash the imperium kernel. After that everything worked with root, though I still can’t get the twrp recovery to flash properly. Having root is good enough for now though.
EDIT: just now got TWRP to flash using flashify, so everything works. On to unlocking...
Click to expand...
Click to collapse
May I ask where you downloaded the Imperium_Kernel_G4_H811_v4.8a.zip
Did "fastboot boot twrp-3.0.2-0-h811.img" work?
What version of SuperSu did you install? I am planning on using "SR1-SuperSU-v2.78-SR1-20160915123031.zip"

king200 said:
May I ask where you downloaded the Imperium_Kernel_G4_H811_v4.8a.zip
Did "fastboot boot twrp-3.0.2-0-h811.img" work?
What version of SuperSu did you install? I am planning on using "SR1-SuperSU-v2.78-SR1-20160915123031.zip"
Click to expand...
Click to collapse
You can get the latest Imperium kernel (5.0 currently) from: http://forum.xda-developers.com/g4/orig-development/kernel-imperium-kernel-g4-v1-0-t3282915
Yes, fastboot boot from the twrp image was kind of a hack, but it worked. As for SuperSU, I tried v1.94 and SuperSU-v2.76-20160630161323.zip. Both soft-bricked the phone. Maybe the newest SuperSU will work, but I wouldn't count on it given that several previous versions didn't.

theprof7 said:
OK so I finally got root. The key was to copy over this file to the phone's internal memory:
Imperium_Kernel_G4_H811_v4.8a.zip
Then:
adb reboot bootloader
fastboot boot twrp-3.0.2-0-h811.img
Then in TWRP, flash the imperium kernel. After that everything worked with root, though I still can’t get the twrp recovery to flash properly. Having root is good enough for now though.
EDIT: just now got TWRP to flash using flashify, so everything works. On to unlocking...
Click to expand...
Click to collapse
I need to flash twrp and root from 20p also. One question to clarify exactly what you did,
Did you originally try flashing TWRP from TWRP? You said you flashed root from TWRP but I want to verify if you tried flashing TWRP from TWRP like:
> adb reboot bootloader
> fastboot boot twrp-3.0.2-0-h811.img
then in TWRP:
> install click on image tab.. then select twrp-3.0.2-0-h811.img recovery and flash it.
> reboot recovery (should reboot to TWRP you just flashed)
Just to be totally clear doing > fastboot boot twrp-3.0.2-0-h811.img leaves your stock recovery intact and just loads TWRP temporarily.
Or did you actually flash TWRP from TWRP and it didn't flash properly?
Thanks!

emailej said:
Just to be totally clear doing > fastboot boot twrp-3.0.2-0-h811.img leaves your stock recovery intact and just loads TWRP temporarily.
Or did you actually flash TWRP from TWRP and it didn't flash properly?
Thanks!
Click to expand...
Click to collapse
Yes, just loads TWRP temporarily. Later I installed some apps that flashed the recovery successfully, either rashr or flashify (I don't remember which)

I hope you have all the files and pc is reading your phone in adb.
Keep the downloaded twrp file in your adb folder with dwonloaded name (Ex:1234twrp.img)
Copy the file and keep in phone internal storage with names recovery.img
adb reboot bootloader (wait for phone to boot in bootloader ofcourse)
fastboot boot 1234twrp.img (whatever your twrp img file name would be)
Now you are in twrp recovery page in the phone.
Tap Install > Images (bottom right) > select recovery.img >
Now you are in next screen where options to slect recovery or boot
Tap recovery and swipe you will see [image flash complete]
Now twrp is permeant. You can restart in recovery without PC. (Tested)
I have flashed more than 6 methods to install supersu. Keep trying and reply.

Stucked in Encryption Unsuccesful help!

I need help, I was trying to root my Oneplus 3T, with stock OOS 4.0.2. After following all the steps, I flashed the dm-verity to keep with the steps, and that worked. But after formatting data, as it was suggested, it gave me an error. It showed like everything was encrypted which shouldn't due to the flash of the dm-verity and now I'm stucked in not a bootloop because the phone actually boots but I cant do anything because the encryption error takes me back to the recovery, which shows an error etc. Is there any tutorial to fully recover the phone from this point? Thank you very much in advance.

Did you try flashing SuperSU after flashing dm-verity? If the zip isn't on your phone at this point, you can go into bootloader mode and use adb to push the SuperSU zip on and flash it that way.
You can use the toolkit to push the files if you want, it'll be easier that way: https://forum.xda-developers.com/oneplus-3t/development/toolkit-oneplus-3t-toolkit-unlock-t3507729
If all else fails, flashing a clean rom always works.

Anova's Origin said:
Did you try flashing SuperSU after flashing dm-verity? If the zip isn't on your phone at this point, you can go into bootloader mode and use adb to push the SuperSU zip on and flash it that way.
You can use the toolkit to push the files if you want, it'll be easier that way: https://forum.xda-developers.com/oneplus-3t/development/toolkit-oneplus-3t-toolkit-unlock-t3507729
If all else fails, flashing a clean rom always works.
Click to expand...
Click to collapse
Now I'm stuck in a bootloop after reflashing stock recovery. If i reflash the boot.img via fastboot from the .zip of the official OOS 4.0.1, will it work? Thank you very much

Not sure why flashing recovery would cause a bootloop. Might be safer just to sideload a fresh ROM. If you're worried about losing files, you can use adb to pull whatever you need first from sdcard prior to flashing.

What I did in a similar situation was to reflash the stock recovery first using the unbrick-toolkit. When booting into recovery then, there is an option "forget password" when it asks you to enter the password. If you select that, it will simply wipe your phone completely and you can start over again.

Serious help needed; completely broken 3T

UPDATE: I was able to install stock recovery through BOOTLOADER (it started working again) and I tried sideload 4.1.7.zip that way. It seemed to work for a while, but unfortunately, sideloading crashed. Same for 4.1.6, update fails around 45%. Phone says INSTALLATION FAILED. Any thoughts?!
Hi guys,
I'm a longtime flasher of phones, but my wife today jacked up her 3T beyond the point that I know what to do. In short:
Her phone was rooted, had an unlocked bootloader and TWRP installed. She updated (despite my endless begging never to do that) the OTA, which crashed her phone. Duh. Not smart. The problem: the phone would not restart the OS anymore. Upon restarting, the phone immediately jumped to TWRP and hung at the splash screen (which takes a while to load, but she doesn't know that). She panicked, rebooted the phone a bunch of times before giving it to me.
I was able to get into TWRP eventually, and figured I'd manually install the newest 3T firmware. This is what I did:
First, I updated TWRP through TWRP, to the most recent version. This was successful. Then, this happened:
Downloaded 4.1.7 from the OnePlus website
Placed it on the phone's internal storage
Went into TWRP, wiped Dalvik, Cache, System etc. (leaving Internal Storage in tact)
Flashed the firmware
I've done this thousands of times, never fails. Except now.
After flashing (which was supposedly successful, as I did not receive error messages), I hit 'reboot' and TWRP told me 'NO OS INSTALLED - WANT TO REBOOT ANYWAY?'
That is bad, right? So, I did not reboot, stayed in TWRP and ended up trying to wipe internal storage, thinking I could then add the .zip with the firmware again later and try flashing again. Just a clean phone, you know? I was wrong. I cannot copy anything to the phone right now, so I can't flash anything (because I can't put anything on the phone).
I'm trying to sideload things now through TWRP (adb sideload) and regular fastboot (either the firmware 4.1.7 or 4.1.6 - I've even tried flashing the stock recovery through fastboot to try and get the stock back, so I can sideload the firmware through there), but nothing works.
If anyone knows what to do, or can give me an outline on what to try, I'd be very helpful. The situation right now:
3T, without OS or ANYTHING on the phone
With functioning TWRP
Only recognized in the command prompt when in TWRP, not when in BOOTLOADER
Phone does not allow things to be copied to the phone via my laptop.
On behalf of my extremely upset wife, I thank you!

@Donaghy
copy the downloaded 4.1.7 to a usb pendrive.
connect it to the phone using otg cable.
wipe Dalvik, Cache, System in TWRP.
select install, storage (pendrive), click on the OOS 4.1.7 zip file.
After the flashing is completed, reboot to recovery (not system).
Phone will boot again to TWRP.
Wipe cache and dalvik, reboot. (ignore NO OS INSTALLED - WANT TO REBOOT ANYWAY?)
If you see the rotating red dot, then all's ok. leave it for 5-10 mins to boot.

Siddk007 said:
@Donaghy
copy the downloaded 4.1.7 to a usb pendrive.
connect it to the phone using otg cable.
wipe Dalvik, Cache, System in TWRP.
select install, storage (pendrive), click on the OOS 4.1.7 zip file.
After the flashing is completed, reboot to recovery (not system).
Phone will boot again to TWRP.
Wipe cache and dalvik, reboot. (ignore NO OS INSTALLED - WANT TO REBOOT ANYWAY?)
If you see the rotating red dot, then all's ok. leave it for 5-10 mins to boot.
Click to expand...
Click to collapse
Thanks for your response. Unfortunately, as per my update (in green, above the post) I have returned the phone to stock recovery. I have tried sideloading 4.1.7 and 4.1.6, but both installations (via adb sideload, via stock recovery) crash around 46%. Phone says installation failed.

Donaghy said:
Thanks for your response. Unfortunately, as per my update (in green, above the post) I have returned the phone to stock recovery. I have tried sideloading 4.1.7 and 4.1.6, but both installations (via adb sideload, via stock recovery) crash around 46%. Phone says installation failed.
Click to expand...
Click to collapse
Try connecting ur phone to a different usb port and then sideload.
If stills fails, get back from stock to twrp recovery and follow the steps i mentioned.
Sent from my OnePlus3T using XDA Labs

Siddk007 said:
Try connecting ur phone to a different usb port and then sideload.
If stills fails, get back from stock to twrp recovery and follow the steps i mentioned.
Click to expand...
Click to collapse
Thanks, I will. I did just realize my bootloader is still unlocked, so this may be causing the crashing of the sideloading of the official firmware (who knows). I am now going to try to lock the bootloader again, ADB sideload the firmware, and then unlock the bootloader again.

Donaghy said:
Thanks, I will. I did just realize my bootloader is still unlocked, so this may be causing the crashing of the sideloading of the official firmware (who knows). I am now going to try to lock the bootloader again, ADB sideload the firmware, and then unlock the bootloader again.
Click to expand...
Click to collapse
Check this, if in stock recovery there is option to install from USB? It it does, then update using otg pendrive
Sent from my OnePlus3T using XDA Labs

Siddk007 said:
Check this, if in stock recovery there is option to install from USB? It it does, then update using otg pendrive
Click to expand...
Click to collapse
I don't own an OTG cable. The only USB option there is, is within the ADB menu in the recovery.
EDIT: locking the bootloader seemed to have made things worse, as I now cannot get the .zip files with the firmware on it to be accepted by ADB/the phone... God, this is a gigantic mess..

I remember there was some adb version (don't remember which one exactly) that had sideloading of large files broken. Try using the newest version from Android SDK.
Edit: just realized you locked your bootloader. Not a good step at all.

C3C076 said:
I remember there was some adb version (don't remember which one exactly) that had sideloading of large files broken. Try using the newest version from Android SDK.
Edit: just realized you locked your bootloader. Not a good step at all.
Click to expand...
Click to collapse
Yeah, some douche somewhere else on the internet said it should be locked. In someone else's thread... I'm trying to unlock it now again through fastboot.
UPDATE: alright, bootloader is unlocked again. I think I have the most recent minimal ABD and fastboot, but I'll check to be sure.

Donaghy said:
Yeah, some douche somewhere else on the internet said it should be locked. In someone else's thread... I'm trying to unlock it now again through fastboot.
UPDATE: alright, bootloader is unlocked again. I think I have the most recent minimal ABD and fastboot, but I'll check to be sure.
Click to expand...
Click to collapse
Btw, which stock recovery are you using?
It should be of the version 4.1.7 you are going to sideload
Sent from my OnePlus3T using XDA Labs

Siddk007 said:
Btw, which stock recovery are you using?
It should be of the version 4.1.7 you are going to sideload
Sent from my OnePlus3T using XDA Labs
Click to expand...
Click to collapse
Whichever is the most recent one that is on the OnePlus website. I downloaded the .img off of their website.

I've had a similar issue, and I tried a billion times on trying to reflash Stock OOS 4.1.0, and sadly nothing happened. I then tried LineageOS by SultanXDA, nada.
So then, I said "Scr*w my data, I'm going to start anew", and I tried the Unbrick Tool, and Voila, new phone with OOS 3.5.X. Not the latest, but it's working.
I suggest you try that mate, you can find it over here.
Cheers!
P.S. - Love your profile pic.

If you sucessfully flashed 4.1.7 then I'd just reboot into system. TWRP sometimes says "No OS installed" if /system was wiped prior to flashing.
Regardless, I recommend you do these things now (if you havent already) and report back:
-Unlock bootloader (fastboot oem unlock)
-Flash TWRP* recovery, not stock. (fastboot flash recovery twrp.img)
-Boot recovery (fastboot boot twrp.img)
-Wipe data + system + cache + dalvik from TWRP
-ADB sideload in advanced section of TWRP
-from your PC: "adb sideload oos417.zip"
-from TWRP: reboot into system (ignore "No OS installed")
If you follow this and its succesful, everything will be fixed
* flash the twrp by xda member eng.stk, not the official one: the only place I can find his TWRP is in the 3/3t toolkit zip. So extract the v5 zip and use the "TWRP_recovery.img": https://drive.google.com/drive/u/0/folders/0B1cephDrsyt_ZzJ1cXpUUlVhSzg
Edit: Instead of doing all this manually, you may want to use the toolkit. See if your device is recognised

Thanks for the help, everybody!
I used the unbrick tool, which worked! I got the phone 'alive' again.
New problem: Right after successfully booting the phone again, I set up the phone (so: clean install, no root, stock recovery, straight out of the box, you know what I mean) and then proceeded to download the OTA that OnePlus pushed to the phone (4.1.7). It downloaded quickly, but the installation has been stuck for almost an hour.
The phone says 'Updating, please wait - do not turn off your phone', and the blue bar is filling. Well, not filling, as it has been stuck at about 10% for an hour.
Is this normal? If not, what can I do? Thanks again!

I turned the phone off and was able to successfully sideload 4.1.7 via ADB. Upon updating, the phone gave me a notification (blue and white letters) that the "DECRYPTION IS UNSUCCESSFUL. The password you entered is correct, but you have to perform a factory reset to use your phone".
So I did another factory reset in recovery, rebooted, and it's up and running, with 4.1.7 on it! I can't believe we got it back from the dead. Thanks everyone, for your help! Really appreciate it!

[Solved]Moto G6 soft bricked after flashing Magisk. What are possible causes?

I was trying to root my phone and had already unlocked by bootloader, flashed TWRP, and made a NANDroid backup. I had the Magisk zip from Magisk Manager on my SD card. I booted into TWRP using the commands
Code:
adb reboot bootloader
Code:
fastboot flash recovery twrp-3.2.3-0-ali.img
and
Code:
fastboot boot twrp-3.2.3-0-ali.img
Once in TWRP, I mounted the cache, vendor and micro SD card partitions. I unmounted them immediately afterwards and then installed the Magisk zip file. The reason that I mounted and unmounted the SD card was because, based on me trying random things, it was the only way for TWRP to show the zip file. Afterwards, I rebooted the system, the "Your device has been unlocked and can't be trusted" screen came up as normal, except that where it said "bad key" before, it said "N/A". The device did not move past this screen and instead stayed at that screen. I managed to turn it off by holding the power button for far longer than normal. I then booted my phone into TWRP and restored a previous backup. Is there a potential cause for this? Is there an alternative method of rooting that I'm not aware of?

did you install the no verity boot for your variant?

The only thing I installed was the zip. If it wasn't in the zip, then I didn't install it. How would I install that and where would I get it?

lucror said:
The only thing I installed was the zip. If it wasn't in the zip, then I didn't install it. How would I install that and where would I get it?
Click to expand...
Click to collapse
Check this thread
https://forum.xda-developers.com/mo...oot-magisk-installation-t3816569/post77074751

Will the fact that I have already tried to install Magisk affect the process? I did flash my TWRP backup, so would that have any bearing on the process? Sorry if these are basic questions, I haven't rooted a phone before and I'm trying to be very cautious.

lucror said:
Will the fact that I have already tried to install Magisk affect the process? I did flash my TWRP backup, so would that have any bearing on the process? Sorry if these are basic questions, I haven't rooted a phone before and I'm trying to be very cautious.
Click to expand...
Click to collapse
Nope, you're overwriting the boot image when flashing no-verity so Magisk would be gone anyways.

Okay. Thank you for your help everyone. I'll try that when I get the chance.

Stuck in fastboot after update today

LG G6 (US997)
Bootloader is unlocked
Stock ROM (assumed to be 21C as I only have the zip and kdz files for this version)
Stock Recover; however, I can install "temporary" TWRP (due to encryption issues)
Issue: Stuck in fasboot mode after Magisk update (seems to be an issue with many).
Received a notification of a Magisk Manager update, so I updated it. Once completed, I opened the manager, and noticed there was an update to Magisk, so I updated it also before roboot. Tapped on the "Reboot" button, watched an error-free flash, and then the phone rebooted into Fastboot. All subsequent reboots are identical. All prior similar updates produced no issues, and I've not added any new modules since my last update. I have access to the stock recovery, but I've not tested its factory reset (yet) to determine if it's working properly, but on the surface it seems to be an option.
Note: My phone isn't recognized in ADB, but it is listed using "fastboot devices" so I assume I can use whatever fastboot commands are available.
UPDATE: Managed to install TWRP temporarily, and my low battery situation is resolved. That said, I flashed the latest Magisk uninstaller, wiped cache and dalvik, rebooted, and it went into fastboot. Went back into TWRP, flashed Magisk 20.1, rebooted, and it went back to fastboot.
What's next? Flash the ROM and boot.img?
And for what it's worth, I still cannot see my phone via "adb devices" but can via "fastboot devices"
Note: I'd rather perform a method that doesn't wipe my data, but my critical data is backed up, so nothing would be lost in a clean flash, even if a full restore would entail some work. From what I've read - and because I have the ROM-21C zip and kdz files - I apparently have other options; however, I'm not entirely sure what issues might arise, but I'm guessing I could 1) extract and flash the boot.img, then reinstall Magisk, or 2) flash the entire 21C ROM kdz, then reinstall Magisk, but I don't know what the pros and/or cons are to either approach.
Any suggestions or links that might prove helpful given I'm stuck in fastboot without access to ADB would be appreciated.
Thanks.
Edited to remove now-irrelevant information from my original post (resolved) that weren't specifically related to the Magisk update.

I thought i am the only one stuck in fastboot after updating magisk on my LG V20. I clean flash rom that i am currently using. Guess i have to stay on previous version of magisk

Faced the same problem with my stock LG G5 H850 8.0.
Using the LG tool "LG Bridge" and performing an update using it repaired my device and i was able to boot again without any data loss.
I'm now trying to install the 20.2 on a second H850 using latest TWRP with no success. (Digest failed to natch on... .Aborting zip install: Digest verification failed Error installing zip file ...)
Is this because I'm running 8.0?

toot-217 said:
Faced the same problem with my stock LG G5 H850 8.0.
Using the LG tool "LG Bridge" and performing an update using it repaired my device and i was able to boot again without any data loss.
I'm now trying to install the 20.2 on a second H850 using latest TWRP with no success. (Digest failed to natch on... .Aborting zip install: Digest verification failed Error installing zip file ...)
Is this because I'm running 8.0?
Click to expand...
Click to collapse
LG Bridge indicates no device connected in my instance, so I can't do much with it, although I've read where it will recognize my device if I can get into download mode. Unfortunately, it will take my battery several days to die in order to effectively turn it completely off to gain access to that mode.

fletcher969 said:
LG Bridge indicates no device connected in my instance, so I can't do much with it, although I've read where it will recognize my device if I can get into download mode. Unfortunately, it will take my battery several days to die in order to effectively turn it completely off to gain access to that mode.
Click to expand...
Click to collapse
Had the same problem, try powering the phone down, then pressing volume up and then connect the usb cable (connected to your computer).

Magisk Update - stuck in fastboot
I have an LG G6 US997 - tried to update to Magisk 20.2 today 1/3/2020 using the typical magisk manager. Now my phone only boots into fastboot. I can get into twrp recovery. I have tried using magisk uninstaller and I can still only get to fastboot.

toot-217 said:
Had the same problem, try powering the phone down, then pressing volume up and then connect the usb cable (connected to your computer).
Click to expand...
Click to collapse
In my case, powering down requires I either remove the battery (not an easy option), or letting the battery die which will take several days. I have fastboot, stock recovery, and the 21C ROM files (zip and kdz), and I assume can install TWRP temporarily, so I'm wondering what my non-LG Bridge options are currently.

Exactly the same vith my LG V20.... I can't flash TWRP neither, says FAILED (remote: 'unknown command')

UPDATE: Using TWRP(recovery mode still worked fine), you can just Install your ROM again and it will repair the issue. It does not wipe anything!! Although I had removed some of the bloatware from the rom originally, so that all came back. You may also need to run the magisk uninstaller from TWRP.
LG G6 US997
**If you are stuck in fastboot mode..(and want to get to recovery mode/TWRP)
1.Hold Volume Down+Power Button(it will restart after 5 seconds) KEEP HOLDING
2. when you see the first LG screen, release power button and hold again
3. Phone will enter recovery options(if you have twrp, just choose to wipe data(this wont wipe anything, its just how you get to TWRP)
4. Reinstall Rom File or use magisk uninstaller

Here is the ultimate solution https://forum.xda-developers.com/showpost.php?p=81378123&postcount=13 Don't panic!

placidns11 said:
UPDATE: Using TWRP(recovery mode still worked fine), you can just Install your ROM again and it will repair the issue. It does not wipe anything!! Although I had removed some of the bloatware from the rom originally, so that all came back. You may also need to run the magisk uninstaller from TWRP.
LG G6 US997
**If you are stuck in fastboot mode..(and want to get to recovery mode/TWRP)
1.Hold Volume Down+Power Button(it will restart after 5 seconds) KEEP HOLDING
2. when you see the first LG screen, release power button and hold again
3. Phone will enter recovery options(if you have twrp, just choose to wipe data(this wont wipe anything, its just how you get to TWRP)
4. Reinstall Rom File or use magisk uninstaller
Click to expand...
Click to collapse
I can get to my stock recovery using my buttons, so I'm assuming I can fastboot twrp.img over to my recovery partition, and reboot to twrp (via stock recovery screen). I just won't have access to my data partition (encryption issue), but I really don't need to access it anyway. I 'think' I have the Magisk 18.0 zip on my SD card, and if so, I thought maybe I could flash it, and see if that fixes the fastboot issue. Just not sure if that idea is sound, and I don't want to make the problem worse, so I'm holding out for some opinions on that idea. I would consider uninstalling Magisk, but I can't see my SD card when it's in my backup phone, and ADB won't recognize my phone (only fastboot does), so I can't copy anything to it unless there's a way to copy files to the SD card using fastboot. I'm thinking it's either a factory reset in stock recovery (if in fact that will fix my fastboot issue), or possibly fixing the issue by reinstalling the older Magisk 18.0 I installed initially.

pendgy said:
Here is the ultimate solution https://forum.xda-developers.com/showpost.php?p=81378123&postcount=13 Don't panic!
Click to expand...
Click to collapse
I'll look into that when I get done working. So long as my PC can see my external SD card while in (temporary) TWRP, I should be able to pull the archived boot.img, copy it back to my SD card, and flash it via TWRP (or fastboot). If not, I can't access my SD card while the phone is in fastboot or stock recovery, and my backup phone doesn't recognize the SD card.

Daaamn, I'll lose my mind.. mean, after couple of hours trying to resurect my LG G5.. I tried, so many methods and nothing. uninstal magisk, wipe dalvik, install magisk 20.1, wipe data - nothing etc. I even tried to use my TWRP backup from June and.. It didn't work. I used this backup some time ago, so it has to be good. That's so fcuked up.. Did someone has common problems or someone has got the solution for this situation? When I'm thing about doing all the stuff again. Clean ROM, bootloader, all the ****.. I hope someone will help me or I'll find solution.

Another LG V20 (H915 turned US996 turned H910 - the only way to root the device and keep the radio ) user here. Can confirm, latest Magisk boots straight to fastboot, even when uninstalling magisk. I suspect the boot partition and its backup are thrown out in some devilish bug designed to make us reinstall our ROMs. Very annoying: I can't do a crossword now as I use the toilet!

I'm having the same issue with my H918, but reflashing the ROM did not solve my issues now it says: Secure start-up
Decryption unsuccessful
The password you entered is correct, but unfortunately your data is corrupt.
I never entered a password, or encrypted my data.
When I select the only option which is to factory reset, it goes back into recovery again.
Any ideas?
Thanks,
Rob

I DID IT! I did backup of my broken system from TWRP. Copy it to the hard disk. Then I replaced boot files (boot.emmc and same with .sha) from another backup which didn't want to restore in full option. After this i flashed backup with changed boot files and phone started. Bootlader remain, root remain, my camera mod for G5 is working. Now I'll have to install apps. Daaamn, so many hours.. I hope this solution will work for someone. Greetings from Poland!
EDIT: root and recovery aren't working but my camera mod reamins working. It's weird. So now I'll have to do root, recovery and then install apps which I used.
EDIT2: Recovery is working, sorry for chaos. Now I'm doing backup and then I will instal magisk 20.1

pendgy said:
Here is the ultimate solution https://forum.xda-developers.com/showpost.php?p=81378123&postcount=13 Don't panic!
Click to expand...
Click to collapse
I can confirm that this worked perfectly on my LG G6, and is much easier than the machinations everyone else is trying. Thanks @pendgy!

frohro said:
I'm having the same issue with my H918, but reflashing the ROM did not solve my issues now it says: Secure start-up
Decryption unsuccessful
The password you entered is correct, but unfortunately your data is corrupt.
I never entered a password, or encrypted my data.
When I select the only option which is to factory reset, it goes back into recovery again.
Any ideas?
Thanks,
Rob
Click to expand...
Click to collapse
I got it fixed. The Data partition had to be formatted, not just wiped.

RESOLVED: For whatever reason, and after one of several temporary flashes of TWRP (mostly to allow my phone to charge), it started mounting the /data partition, something it had never done before due to the encryption issue on Oreo I could never get past despite several suggested solutions. I even managed to create a backup of my /data. In any event, I uninstalled Magisk, but it left my ramdisk corrupted, which forced it to fastboot (probably why all other attempts to fix this failed into fastboot after the Magisk update). Decided to flash my ROM which fixed the ramdisk, flashed the no-verity/no forced encryption, then reinstalled Magisk v20.1. All was well and good after that with no loss of data, and TWRP persisting in recovery.

[HTC ONE M9] magisk error ,cant uninstall or install again
Hi, I need some help with the my phone was have problematic work on magisk .zip. When I rooted my phone I installed the best latest version of magisk - 20.1. Beta for HTC and Android 10 but installation is not going well, probably not installed or something wrong, because when restarted phone, magisk is not exist in the phone and is not rooted .
So I trying to make sure and use magisk uninstall zip in twrp 3.1.1 but is not possible to uninstall, so trying terminal and unimod and/or mm commad - not found this command , module etc.
Try install 19.0 version magisk but all install metod finishes wit errors .
Dont have magisk now .