e.g. until recently, you couldn't install ESXi on a Gen9 BL460c with the UEFI BIOS -- you had to configure it with legacy boot. That has been fixed in a firmware update. Overall the G9s were very flakey -- if I rebooted 6 of them, 1 of them randomly wouldn't come back and it would be stuck at some phase of the POST. Power cycle it, and it would boot fine.