i think some optoins in your Uefi motherboard failback to CSM / MBR mode
can you recheck in your UEFI motherboard
- secureboot desactivated
- no CSM
- no legacy
- no fastboot
- all disks are ont AHCI ( not raid )
if you boot on USB , you should see
Uefi: < USB vendor name > < partition > → select this for boot UEFI
under live iso , you can check
inxi -Fxza
test -d /sys/firmware/efi && echo efi || echo bios
sudo efibootmgr -v
sudo parted -l