Far easier than I first thought:
Booted the Mac mini 2011 from its HD, put in a bootable USB-Stick, prepared with balenaEtcher, restarted with opt-key pressed, choose EFiBoot, stepped through the Ubuntu install (nice one: ssh-server is an opt-in in the process), rebooted and ... got my promt, connected via iTerm from my Mac, next will be setting up the FMS now
4 Likes