The Talos Principal 2 demo is available in Steam now, the full game comes out in November.
https://store.steampowered.com/app/835960/The_Talos_Principle_2/
But since the games is officially Windows only, it won't let me download/install the demo (because linux).
Why Steam?!?? You're going to let me use Proton to play the full game sp why not allow the demo to run the same way?
If anyone knows a work-around I'd be very happy.
EDIT: The suggestion by @ECCTM worked very well and I've started playing the demo. It "just worked".
SECOND EDIT: I started a new Community for discussing the whole Talos Principle series, for anyone interested.
Valve should consider making it the default at this point, and just give the user a warning the first time they launch a non-supported game. Because these issues happen often enough that people may be left with a bad impression of Linux (and Steam) game support.
Also the games work flawlessly or nearly-flawlessly over half the time anyways
I've only ever had to deal with this issue when it comes to installing a demo of something. Generally Steam already knows if there is only a Windows build of a game or not and acts accordingly. If this is the thing that causes a bad impression of gaming on Linux, then you've probably already overlooked (or been blind to) other annoying situations.
You must already have the setting enabled (as do I). But on a new install of Steam, only games that have been approved by Valve will run. And that's using the old system, and not the new system that the Deck uses. So there's is only a small amount of games supported.
Removed by mod
They already do this with the deck verified system. I'm not sure how it would be more of a problem on desktop.