Antitrust is not about preventing big companies making money. It’s about preventing specific practices by monopolies to restrict the free market and to abuse their users. Don’t get me wrong, there’s a ton I find morally objectionable with companies as big as Valve and people as rich as Gabe. We might agree on those issues. But this particular Google thing is about something else. And Valve is indeed different to most tech companies in that regard.
I’ve gamed on Linux for the past 5 years. If you use Steam, most stuff works out of the box after you enable a single setting. Now that the linux gaming community is growing it’s easier to find workarounds for the games that don’t work. The only games that are hopelessly broken right now are games with intrusive anti-cheats that don’t support Linux. You can head over to protondb.com and check compatibility status for your games, including workarounds when necessary.
If you don’t use Steam, then I’m not sure. Last time I played non-Steam games there was more troubleshooting and tweaking required but it’s been a couple of years and I don’t know the current state. It’s worth noting that Valve’s compatibility layer, Proton, is open-source and based on other open-source projects. There’s work currently being done to port the functionality outside of Steam. Hopefully, this will mean that in the future all launchers will behave similarly.
But that’s just the software side of things. Don’t forget to check how your hardware works on Linux as well.