Steam is available and runs great. Valve has really put an insane amount of work into making Linux gaming smooth and painless. They have their own flatpak equivalent called pressure-vessel that steam uses by default, and everything that steam supports in Windows is 100% supported in Linux as well. If you check out protondb.com you can put in your steam account name and it will scan it and tell you any games in your library that will have issues in Linux, but outside of a few of the competitive shooters that have super aggressive anti-cheat generally everything either works out of the box, or after some minor tweaks (typically adding a few launch parameters).

Additionally, there’s an excellent unified launcher called Heroic that lets you connect with and use the GOG, Epic, and Amazon Gaming stores, and provides a convenient wrapper around Wine/Proton for actually running the games.

Finally there’s another launcher called Lutris that a lot of people swear by and supports some of the less used stores like Itch.io, although when I tried it recently I ran into some problems getting it to work.