If you get the error message: This PC can't run Windows 11, This PC must support UEFI Secure Boot. Then you are right here! We'll enable in this tutorial UEFI Secure Boot for legacy Mainboard BIOS. I'll show a MSI Motherboard with a AMD CPU, but it also works for Intel and other Mainboards. All Mainboards have the same main structure, so don't worry.
Links:
Enable TPM 2.0: • Windows 11: How to Enable TPM 2.0 in ...
Install Windows 11: • How to install Windows 11 ISO from US...