Most games that work on Steam Deck aren’t technically Linux-compatible and therefore have no “Linux support” needed. Proton has come very very far, and most games are running the Windows exe through Steam using Proton.

In fact, I’ve played several games that do have native Linux support, and they still play better using the Windows version through Proton. On my Steam Deck, and on my shitty non-gaming laptop.

So no, they don’t have to support anything new.