I finally tried rebooting the affected server, and as I expected it wouldn't boot with 'no bootable device available', and I was able to recover it by upgrading (admittedly ancient) BIOS (EFI) to the latest available version.
I finally tried rebooting the affected server, and as I expected it wouldn't boot with 'no bootable device available', and I was able to recover it by upgrading (admittedly ancient) BIOS (EFI) to the latest available version.