bleepingcomputer[.]com/news/security/msi-accidentally-breaks-secure-boot-for-hundreds-of-motherboards/
neowin[.]net/news/beware-windows-11-system-requirement-secure-boot-broken-on-msi-motherboards-full-list-here/
MSI released a new version of the BIOS firmware for Very many of its motherboards in January 2022. The BIOS settings available vary by make and model of the motherboard. MSI has a setting [Image Execution Policy] that disables Secure Boot, even though it's turned on -- it tells the BIOS to start whatever bootloader, regardless of whether Secure Boot OKs it or not, and that setting is turned on by default. Obviously, in most cases owners of the effected motherboards should check the BIOS settings to make sure it's turned off & Secure Boot is working.
BIOS settings in general tend to be a nightmare, since there are no standard terms, or locations in the BIOS settings menus for many of the settings -- it's common to have a setting that does the exact same thing in every BIOS, but goes by different names & is located in different sections of the menu. Then add the various eccentricities of the engineering team behind any given BIOS -- on the Asus m/board in my wife's PC, the nonexistent motherboard RGB lighting has to be turned on for the power LED to work (!). At any rate, that kind of explains why the security researcher who found the problem had to jump through a few hoops to find out what was going on.