oh weird, I swear it was boot looping and I tried multiple times, but when trying to enter recovery I randomly hit the volume up button after the boot continued after the corrupt message and it succeeded. I'm slightly worried though since I have no clue what just happened hmm
EDIT: first thing I'll do is enable OEM unlocking. just in case ...
EDIT2: just confirmed that it's still using the same slot and rebooting works. The "device is corrupt" message stayed, was that the "normal" one when booting? I was sure the behaviour was different, like I need to actively click through it now, while before it would continue booting without that. I'm starting to question my sanity, I guess it was never bricked after all 🤦♂️