I've gotten it to work on Windows 10 by booting into live Linux and renaming the Windows Defender folder in Program Files. No clue if it would work on 11.
I am surprised that ever worked. I was confident Win10 did verification that system files were in place and matched a hash or some other integrity mechanism.
They put in a lot of effort to prevent you from deleting the main executable (you the user that is, malware can probably delete it just fine using the usual methods) however one day I discovered you can delete the .dll files from its folder and it no longer runs, and Windows does not do anything to try and fix it.
you can also set the permissions on it so SYSTEM can't execute it
You can ask it to with things like SFC but fortunately it's not that locked-down yet... and of course you can always patch those checks out if the OS itself isn't running to interfere with you.