This keeps getting brought up, but the reality is that there is nothing special about SteamOS 3. If people want a SteamOS-like OS (Immutable, Steam/Proton integrated, Steam Big Picture as Primary interface), then it already exists. Chimera, Bazzite, probably others. The only thing Valve could realistically improve on is the installation experience.

SteamOS’s only real advantage is that it is hardware restricted. Valve is able to test against a narrow field of hardware and insure a high degree of stability because of it.

The Nvidia open-source driver situation has been improving. Supposedly Valve has been working with them on it alongside their ARM support.

You can also try your hand with the closed source drivers but ymmv.

I’m tossing in another vote for Fedora. It’s honestly about the closest you’ll get to “Standard Linux”.

It’s one of the most bleeding-edge distros while still being very stable and secure (Rolling Releases are more up-to-date but I’ve had enough issues with them). Traditionally a Gnome-First Distro but the word is that the next release will promote KDE alongside Gnome (That said KDE is already great on it).