I restored the old BIOS, still no luck. The PC boots straight into bios after idling around for 20-30sec. The bios shows me both m.2 drives, but the F11-boot-manager shows nothing. At best, it shows me an attached USB stick, but when I try to boot from that (eg. a Ventoy stick), I get a Security Violation, followed by the Shim UEFI Key Management:
but I have no clue what to do there.
I guess I just killed my PC 