@Hawkeye
W11 requires secure boot to be enabled to boot along with tpm, fast boot can and is usually disabled,
but must be present for W11 to boot, along with a gpt formatted drive. So, I doubt you will be able to
disable W11 secure boot, without permanent damage to W11. My best advice would be to run Linux
in a VM, ditch W11 and install W10 or ditch W11 all together and run Linux. Their is no win win situation for this.
I checked my W11 secure boot status, and it is indeed disabled, but I have home built
PC. It more than likely is what @squealingcode is saying, and it has been altered by
the manufacture with the keys to enable secure boot. I still say if you disable secure
boot on that machine, W11 will probably not boot.