[Huawei P20 Lite ROMs, Kernels, Recoveries, & Other] V10lator:
Thanks for the suggestion but that won't work for me for various reasons:

- The harddrive with the backup of the recovery partition died some years ago, so no way to flash it back.

- When flashing TWRP the phone will always boot into it cause Magisks boot to recovery magic seems to be still there. Only way to stop this is flashing Magisk back.

- I want my phone to be rooted.

- I want to use Magisk modules.

- I want to use XPosed modules and the way to do that without breaking safetynet is through Magisk/zygisk/LSPosed.

For now I exchanged some apps (like the launcher) + am using some XPosed modules to better performance and battery draw but that works to a small extend only. So I guess all I can do now is to wait for either AOSP 13 to become more mature or Magisk getting an update (depending on where the root of this issue is at).

//EDIT: Purchased a new SD card as I thought the old was damaged but the new one shows the exact same issues: The phone crashing after a short moment of power on time when the card is formatted as internal memory.

So I did a bit more research and finally uninstalled Magisk but that made things worse: Now the old bugs are still there (hard to tell how performance/battery is right now as the phone crashes all the time, so take this with a grain of salt) + new ones:

- Phone randomly blackscreening.

- Phone randomly not unlockable (just showing the background image and the status bar on the lock screen).

- No app starts anymore (tiping on the icons just does nothing -- was too fast with this, it's just some apps but that freezes the launcher icons, so after tipping one bad app none is launchable anymore. Anyway, the apps who launch freeze at the splashscreen).

- The Launcher randomly freaking out (just a black screen with status and navbar but no icons or anything).

- Phone discharging while beeing connected to the wall charger (could be a symptom of the device having more boot time than power on time right now thanks to all the crashes and issues).

- Phone refuses to connect to WiFi. -- scrap that, was my routers fault.

So now the phone is completely unuseable for me!

//EDIT²: Okay, the crashes and apps not launching are gone with removing the SD card. Still I need this card as internal memory is way too small, so what to do now?

//EDIT³: Did a bit more research and here's a logcat from removing the screen untill around 2 minute frozen (untill I decided it's enough useless logspam) : https://public.nbg01.v10lator.de/logcat.txt

Also a better description as this isn't really a crash but a warmreboot + boot never finishes, so the device just jumps to the huawei bootanimation (seemingly skipping the bootloader) and then plays the boot animation forever (not looping).

Hope this helps.

//EDIT⁴: Looked into the logcat for myself and here are (a few of, hard to remember anythoing after hours of reading) my findings:

- Repeated warnings about "slow operation", so slow that frames get skipped and stuff.

- No hardware audio/video codecs but software fallbacks.

- Complainings about important files missing on the system partition.

- Not reading some ANE specific file from the system partition for whatever reason.

- The NFC daemon beeing in a crash loop (this is LLD-L21 specific (and most likely also true for other ANE compatible phones who have no NFC hardware) but causes a lot of load, so will see if I can fix this with a Magisk module).

- vold eating 100% CPU on one core untill suddently a ****load of system apps crash. This is the crash I was talking about. I still can't explain it in any way through. A wild guess is that it's somehow connected to the NFC daemon crashes as these are causing issues like aborted broadcasts. The phone might just get more sensible with an SD card inserted or vold is spinlocking waiting for a broadcast or something?

Remember: The logcat was taken without Magisk.

//Next EDIT: Readded Magisk and created a module completely disabling NFC: Performance is better but vold still freaks out, leading to a system crash. I'm out of ideas now, so waiting for your reply.

//One more EDIT: To sum things up, these are my findings:

With Magisk:

- Randomly hangs while rebooting.

- Randomly blackscreening.

XPosed issues:

- Not all things working like expected. This might stem from the XPosed modules needing to get updated through.

Without Magisk:

- High CPU load.

- Bad battery performance.

Unrelated to Magisk:

- Vold freaking out when SD card formatted as internal memory, crashing the whole system.

- No hardware audio-/video codecs used, leading to frameskip and stuff when watching videos.

- SafetyNet not passing.

- Some minor issues logged in logcat where I'm not sure if these are even real issues.

Maybe even the "with Magisk" things are unrelated to Magisk but I didn't test long enough.

Anyway, the biggest issue / highest priority for me is the one with vold.