it’s like MacOS where if it’s a game not on Steam then you’re shit out of luck if there isn’t a Linux specific version?

No it’s not. I don’t even have Steam installed & play games just fine. You can use Bottles or Lutris to run the games, I recommend Bottles. The downside is that you’ll have to learn how to use these tools. For example you’ll not only need to fiddle with settings, but also with dependency dll files. Chatgpt can sometimes help & tell you which dlls are needed by which game. (at least when I asked it about Oblivion Remaster & Horizon Zero Dawn it knew)

Lutris has the advantage of community installers where you don’t have to figure things out, but it’s annoying that they’ll force you to log into Gog Galaxy and such for your downloaded installers & Lutris may not have a force offline sandboxed mode if you don’t want the software you run to report home.