mstsc.exe was exactly the one I used. I vaguely remember that I had used that successfully some years ago (in a much bigger environment with proper certs) and it worked.

Regarding NLA: I believe that I would have to disable that on purpose no? It was on a very vanilla Windows 11 install. I just looked and regarding any other settings than the ones listed in mstsc.exe, I get told that Windows 11 Home edition doesn’t support RDP lol.