As a longtime Debian Stable user, I can attest that gaming on it works just fine, whether via Proton or natively.

It was rough at the first half year or so after Steam Linux client launched where system libraries were simply too old and one had to smuggle in libc from Ubuntu, but that got solved by the next Debian release, and it’s been smooth sailing ever since. :)

Of course, I wouldn’t recommend Debian for a gaming system for a newbie. It’s just what I’ve been using as my daily driver for decades, so I did not want to switch to something else just for something as unimportant as gaming.