I wonder if it has anything to do with this:
https://askubuntu.com/questions/1418992/sgx-disabled-by-bios-message-on-ubuntu-20-04-booting
I’m not familiar with SGX, but it kinda sounds like a predecessor to Secure Boot? I wonder if that’s preventing some kind of startup.
That link I gave mentioned a Grub setting for ignoring SGX. Maybe try that after updating your BIOS, if that doesn’t work.