I’ve been using Ubuntu for a while now, and was planning for my new build (Within the next week or two) to try out PopOS (Which is still based off of Ubuntu).
If I was more familiar with Fedora, I might have tried out Nobara, (but it doesn’t have the support that PopOS does yet).
And considering you use Nvidia, I’ve read that PopOS makes it easier to get drivers for that. If you’re still new, either PopOS or base Ubuntu would work, but PopOS might get you set up faster. I wish I could give a more detailed answer.
There are a few open source game projects I follow. I suppose the most famous one is the Freespace 2 source code project. Although it didn’t start open source, the original devs open-sourced it later. It has great support, and a great modding launcher called Knossos. To play the game, even with the source code, you either need the original disks or a copy of the installer from GoG, but it’s really cheap. Getting it working on Windows is pretty easy, but Linux is only slightly more complicated. (Fortunately, there’s a new launcher that makes it way easier).
If you’re interested, let me know.