Just to check if you are indeed booted into efi
[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS
Then on to that line about ‘not supporting’ … well you would have to consult your documentation for that.
It could be totally true that you have no supported access to your UEFI/BIOS. Horrendous, but true. Only the MOBO manufacturer (and you) know.
The same goes for any possible ability to get into it… maybe you need to use a special key or something.