https://ubuntuforums.org/showthread.php?t=2291335&p=13341757#post13341757
I guess you could try loading secure boot defaults....or deleting secure boot and then loading the secure boot defaults. Or maybe even try loading the BIOS defaults (F9) and then save/exit (F10).
I'm sorry but I'm out of ideas. One other thing that I forgot to mention was I disabled Windows fast startup, but that shouldn't be related to your problem.
