Oh wow, the #android BS gets worse and worse and worse, the hole ever deeper.
I installed Magisk. That meant to mess around with adb, fastboot and speculatively patch roms based on vague information. I figured that would be the hardest part on my path to microG. Apparently I was very very wrong.
Signature spoofing is required and it is either enabled (no) or there are a couple of ways to do it. Something called Xposed, but whatever it does, my system is not supported. Other ways are ...
@RustyStriker My life is not googled. I run LineageOS on that phone. Unfortunately LineageOS does not support singature spoofing, which seems to be required for microG to work.
There is a LineageOS fork that already comes with microG and it is supposedly possible to migrate to that from regular LineageOS.
Just how that migration is supposed to work I have no idea.