As the others have said, odds are you only need to flip the switch in steam to ignore OS. I've been overwhelmingly happy with how many games work this way.
To the point that I'm far more likely to find a game with clunky default controls on Steam Deck than I am one that won't play. And learning to use some of the more advanced control features of the system goes a long way to fixing that.
> And learning to use some of the more advanced control features of the system goes a long way to fixing that.
I need to take the time to do that some day. I’ve seen people swear Factorio was playable and fun on the deck, but the controls were just always too much of a struggle to get working in a way that worked for my brain.
I could play, but I just couldn’t get it smooth enough that the controls got out of my way.
I’d love (and hate) to have Factorio playable on the steam deck.
If it's been a while since you last tried it on the Deck, you might want to try again since recently they've added official controller support.
I had managed to get used to the Steam Input mappings so my experience may not reflect too much on you, but the official mappings are also pretty nice. IIRC they also show control hints underneath the map for context-sensitive actions, which help a lot too.
I think there's a switch to flip in Steam's settings that allows you to use any game with Proton even if untested/unsupported. (Something to that effect, can't look now)
If you go into a game's properties in Steam (the little gear icon), and and then choose "Compatibility" from the resulting window, you can choose a version of Proton to run the game, usually the latest stable is good, sometimes you have to play around to find a good version.
Once you've chosen a Proton version, the option to "Install" will be available in your game menu.
I gave up on Windows a couple years ago, and most Steam games run in Linux using Proton through Steam. Some modern titles with fancy DRM don't work, but I generally don't buy those anyway (Denuvo, certain anticheats, etc).
For non-Steam games, I do the same thing, either with Steam (by adding a non-steam game installer, and using proton to install it), or by using Lutris (https://lutris.net/). I generally use Lutris with my GoG library.
Then realized it doesn't support Linux. I can't install it. I was shocked.
And then I realized how crazy it is that I had presumed a game would run on Linux. How far we've come.