I didn't really point much out. I only know that multiplayer games use either Steam or GOG Galaxy to log in and that there aren't many more OpenXR runtimes besides SteamVR on Linux (I know of WiVRn, but I had an Nvidia GPU and couldn't figure out how to compile the Vulkan extensions required). I find it tedious to manually set up save file synchronization for my GOG games, so I really can't be arsed to go so far when Steam just does it all for me.
Are you sure that you're using the proprietary Nvidia drivers and not nouveau? Check if nouveau is blacklisted in /etc/default/grub and see if it's running with inxi -Fxz in the "Graphics" section.
I do the exact same, but I also buy multiplayer and VR games on Steam, because I run Linux, and GOG Galaxy isn't out on Linux (yet). I really don't want to faff about getting all of that working on each individual game. I bought Rain World and FTL on GOG, but Star Wars: Battlefront 2 on Steam.
I've got this idea that's been in my head for a long while, the gist of it is this: "What if Celeste had guns and/or fighting game combos?"