1. Verify if /etc/fstab mentiones efi
2. If yes, check mode of ubuntu install:
open a terminal (Ctrl+Alt+T) then type the following command:
[ -d /sys/firmware/efi ] && echo "Installed in UEFI mode" || echo "Installed in Legacy mode"
3. if "Installed in UEFI mode" is seen, then to access UEFI BIOS, type in:
4. sudo systemctl reboot --firmware-setup