AMD open sources their drivers too.
Ah, right, duh.
Ok so yeah, uh... the Z2 Extreme supposedly is going to have some kind of 'AI' functionality or additional component... god knows what that means...
Theoretically it could be more difficult for open source devs to fully leverage that, even if the drivers are open source...
But yeah, for the rest of it, it probably would not take much time at all given that Bazzite and SteamOS already run on the last generation of the same chips.
EDIT: On second thought: I wouldn't put it past MSFT to go out of their way to invent an entirely new input controller interface for the buttons and thumbsticks and such, that would require open source devs to reverse engineer it a bit to properly interface with it.