[14:59] <enyc> Hrrm
[14:59] <enyc> ubiquity on 22.04 does  Legacy boot in GPT ....
[14:59] <enyc> Creates a BIOS boot partition, fine
[15:00] <enyc> However,  it neglects to set a 0x80 "bootable" flag anywhere in the protective-MBR,  which means some BIOSes (notably "intel desktop boards" including a NUC I have here) will refuse to boot the disk.  Such bioses not only look for 55 AA  but require an 80  in one of the primary partition slots (a partition marked bootable).
[15:01] <enyc> Known limitation/"bug" ?