I've never done serious Linux gaming but Lubuntu is lightweight and fairly responsive even on my old 2009 laptop.

If gaming is the primary thing you are going to do on it and everything else secondary. I can be helpfully unhelpful. There are a number of distributions based around valves steam OS. Which is at its core. Is what's running on the steam deck. Not 100%. But very close. They will give you a very similar experience and feel to the steam deck. Only allow you much more hardware choice and larger displays. So I

I've been running MX Linux four a few years mostly for playing games and I've had great success with only one game that caused issues, and one that wouldn't play due to anti-cheat software.

Just enable the high end hardware repos on install if it's a newer system and use proton for minimal hassle.

Please just do yourself a favor and run Linux mint cinammon. It is the easiest distros to use bar none and super reliable, great for anything gaming included. Tons of support and hell and software options and driver support.