It really all depends what we're talking about when we say "gaming" tbh. Proton on Steam will run literally thousands of titles in one click, no configuration necessary, flawlessly. But thousands of titles isn't all titles. If you're a gamer who is happy to play what works and miss out on what doesn't, there are enough games on Linux to keep you playing for a hundred lifetimes. But if you've got a specific competitive multiplayer game in mind that implements anti cheat, or you want to play all the biggest AAA releases as soon as they come out, you're going to have a less positive experience.

And yeah, Nvidia on Linux can really suck, too. Anybody buying/building a rig with Linux in mind should steer well clear. If you're talking about an existing machine with Nvidia then you might get lucky and have an easy straightforward time, or you might find yourself straight in at the deep end with a crash course of Linux sysadmin...