That's really what the (Deck/Machine/SteamOS) Verified program is for. Valve tests games out on those platforms and reports results back for everyone on the store page. Publishers have the control to explicitly mark it as unsupported too.
reply...I mean, you're buying a windows version, then complaining that it's not running well on an unsupported operating system?
replySteam is very upfront when you’re buying a windows game on mac. There’s a big banner saying it’s not for your OS and likely won’t work. There’s a compatibility icon for mac, and it’s filterable, for library and store, so you can get mac games. There’s an additional click-through screen on the store page with a checkbox. There’s a lot that’s filtered out!
replyThe proton story pretends like you can run every windows game on steamos, verified or not. It’s quite different and tbh a little dishonest. I wonder how much of it is avoidance of alert fatigue (because many many unverified games do work) and how much if it is trying to sell users on steamos.
Well, just remember that Steam doesn't actually know where you intend to play the game. I buy most of my Steam games on my phone, and obviously there's no point in steam warning me that the game will not run on android.
reply