> "games that market is mostly concentrated on is the single category that still does not work on Linux."

Yeah. That single category is "games that the devs have done the extra work needed to make them not run in Proton". There's no consistent game genre, age, or intended audience... it's just whether or not the dev decided that running on the Steam Deck, SteamOS, and the various Linux distros was something that they were actively going to block. [0]

[0] An illustrative case is Apex Legends. It waffled back and forth between "permitted to run under Proton" and "not permitted", and eventually landed in the "not permitted" bucket. And no, "'competitive' shooters" is not the category that this fits in because shooters like Hunt: Showdown and Counterstrike work just fine with Proton.