ok, MiUI rebootet the moment I posted this.
now I tried unlocking it with the Mi Unlock tool, but it doesn't show any device...

Hey,
I didn't unlock MiUI before starting the wipe and installation with UBports, now my phone is stuck at this fastboot screen with that communist rabbit fiddeling with an android. its not recognized by neither UBports nor android platform tools. can't reboot or do anything with it, its completely frozen. sorry for being so stupid, I hope there's a way to get out of this...