ah crazy, i made it work with Ubuntu 22.04.4 LTS!
For some reason i had to unplug the PC before restarting. Then it got found as UEFI and could boot.
The full installation on the USB was a bit dirty, as i put the Live Ubuntu in a Virtual Machine and installed it from there. So i typed the full disk encryption and login passwords in Windows … but I wont be too paranoid about that one now 😅
could solve it: https://lemmy.ml/comment/8727647