Think you need to change the secure boot bit.
I found these quite useful (like about 2 hours ago -
https://www.windowscentral.com/how-enable-secure-boot-pc-install-windows-11
https://www.windowscentral.com/how-convert-mbr-disk-gpt-move-bios-uefi-windows-10
https://www.youtube.com/watch?v=u2TIUFl53ZY
https://www.youtube.com/watch?v=R7-7rY8uTTk
I think it might depend on how the storage you operating system is formatted - MBR or GPT.
Still, having followed the above (I think) my PC may still not be compatible (and it should be, again, I think).