[OnePlus 6 Guides, News, & Discussion] Fevves:
Status: Solved (somehow)!

Bear with me... please?

I was on stock 5.1.11 OOS, Android 8.1, rooted with magisk 21.2 with blu_spark kernel and blu_spark TWRP while suddenly, out of the blue my phone rebooted (after 2 years of usual use and without any glitches) and I was cut off from everything.... I lot all my photos and videos... (being an idiot and not having time to back them up to my PC).

Story shortened: I could not save my data and my user files, nor anything (I had PIN locked screen and somehow the inherent locking files in data/system got either damaged or corrupted so TWRP was not decrypting the partitions even with the right password). I tried all that I knew to revive the phone, but my TWRP backups (all of them!) failed wih error 255... so after a soft bricked phone and bootloader, the only option I had is to fastboot flash the ROM, in this case (why not, since my phone, as I had it, was gone) OOS 10.3.7 (partition by partition) and it indeed revived the phone. I somehow managed to get TWRP twrp-3.3.1-18-enchilada-installer-mauronofrio installed and running fine but I can't seem to root my phone as it is erroring on System UI constantly if I flash magisk 21.4.

Which Magisk version should I try and install as I really lost time (havent's slept OK for almost two days) over this. I tried to search all over the forums and web, but nothing is pointing to a working Magisk TWRP flash files for me... all threads and sites are stating to download the latest one... which in my case is not working at all.

ps: I tried with Blu_Spark TWRPS before and I could not find one to work with OOS10.3.7 which is rather strange...

pps: Strangelly my active slot now is A while on OOS 5.1.11 was always B....

Thanks goes to all you guys who can patiently reply.

Edit:

Somehow and after several trials with all different Magisk versions, bootlooping and System UI crashing... topmost issue was these damn blank screens with only white LED flashing on reboot... I got to flash TWRP twrp-3.3.1-18-enchilada-installer-mauronofrio again and this time around the TWRP booted and my active slot was B and not A, so I flashed the TWRP ZIP, rebooted recovery... it sticked... I flashed the complete OOS 10.3.7 zip... rebooted to recovery, flashed Magisk 9.14, rebooted recovery, checked and still on slot B... flashed kernel, rebooted to recovery, still on TWRP... rebooted system and I finally got the system running... and above all I have root and custom kernel installed while TWRP sticks ok.

Now...

The issue is my fear to update Magisk through manager etc... but I observed repositories has almost zero modules I want, such as Greenify, Viper, Ed Xposed...

I did performed backup procedure through TWRP of all partitions so I can revert (hopefully) if something goes bad again. I haven't set any kind of screen lock and I'm using swype up for the time being.

Anyone care to provide me with an advice?

TIA.

Edit2 on January the 23rd 11:04:

I updated Magisk directly form the Magisk manager in the OS (not the TWRP), crossed my fingers and now I'm on Magisk 21.4, Magisk manager 8.0.7, have working and sticking TWRP twrp-3.3.1-18-enchilada-installer-mauronofrio, and can finally proceed with "my life" (aside the loss of my user data). I hope this post might help someone else not to give up and to persevere and fix their phone.