I'm thinking of buying the Raspberry Pi 400 and I see Ubuntu MATE indeed has a 64-bit Raspberry Pi port. While the "400" apparently has some compatibility issues in some scenarios, it's essentially a higher clocked Pi 4. Assuming it's working, I wonder if it's performant as a Raspberry Pi OS alternative to the official distro? I think I prefer a cleaner MATE over the default stuff.

Edit: Oh I see now I essentially posted in parallel with another question about the Pi running this. Well, there are images for it at least!