[LG G8 Questions & Answers] Jimmynidas:
Hey guys,

I'm currently stuck in a fastboot loop after trying to install Magisk after flashing the Arrow ROM. I believe I messed up when choosing between boot_a and boot_b and flashing the patched img via QFIL. I initally patched boot_a, but when that didn't work I rebooted and patched boot_b. I did this because when I installed Arrow the instructions asked me to select the device slot that was inactive. I thought this meant it was swapping my device slot from A to B, but I probably got that very wrong. I did go into EDL mode and flash my original boot_a and boot_b in hopes it would reverse my mistake, but that did not work.

When I attempt booting the TWRP zip from the lineage guide archive I get this error "failed to load/authenticate boot image". I'm assuming this is because it wants an .img file and not a zip. If I try flashing the same zip file I get this error "Cannot flash this partition in unlocked state".

I did make a backup of all partitions via TWRP before this, but I'm unsure how I'd go about restoring everything. I do have access to EDL mode.

Any help is appreciated. This isn't a primary device though, so if it's bricked I'm not going to be that upset over it. Just something I wanted to try for fun. Haven't rooted a device in years. The G8 was a bit more difficult than I recall, so I'm sure I made a mistake somewhere.

Update 1

I flashed the ABL enginnering file and have some progress. Now fastboot shows my Active A/B Slot. It is set to B now, it was A originally, which I guess confirms that the Arrow OS instructions did switch from A to B. Maybe patching both through Magisk broke the boot image? If I'm understanding this correctly.

Update 2

While in fastboot (Phone was still looping) I entered the following command to change from Active Slot B to A, "fastboot --set-active=a". I've read this could potentially brick your device, but since my device was originally set to A and it was a brick at the moment already I took the risk. Booted into the recovery mode and selected factory reset. It took about five minutes, but I'm now back to the setup screen in the OS. Glad to be back to this point. Now I just need to figure out how to get Magisk Root working without repeating this process.

Update 3

Almost forgot to boot back into EDL, load up QFIL and push the original abl_a and abl_b files back to your phone. Otherwise you won't have any touch input.

Update 4

I seemed to have messed it up again. I tried locking the bootloader back, so I'd stop getting the error message upon bootup. I've decided there is no benefit to unlocking the bootloader and rooting for my purposes. Just wanted to try it out. After doing so I started getting an error stating the device failed security checks, so I pushed the abl engineering file back to the device to unlock it. After I went to push the stock abl_a and b files and decided to go ahead and push the stock boot_a and boot_b to make sure everything was back to normal. Which I didn't think was a big deal, but now I can't boot into the phone without using the abl engineering file.

At the moment I'm unsure what to do. If I push the abl_a and b stock files the phone goes into a fastboot bootloop again. Can't run any commands that way either. I have to boot the abl enginnering file to do so, which in turn allows me to get into the OS but disables touch input. So at the moment I think it's bricked.

If I could find a TWRP image file to flash with the abl enginnering file I could possibly perform a restore from the original backups I made, but I'm unsure where to find one since TWRP doesn't really exist for the G8. I just have a zip file.

Overall not too much of a loss, but the G8 was a great DAP. Hate to lose it. If anyone has any suggestions I'm all ears.