Yeah, very sad. These Macs are probably the best Hardware you can get for small money. My 4.1 and 5.1 Mac Pros running as servers on linux are rock solid. The performance is good enough for my purpose.
Booting was not an issue. Bur UnRAID crashes.
My problem is, I am not familiar with linux and EFI stuff. Normally that just works. I don't habe the knowledge why it crashes.