I use KDE Neon on my laptop and I’d prefer to have KDE as a DE on this one too (if possible) but I don’t mind a non Ubuntu base. Basically I’d just like to be able to play games on it without much hassle but I know how to paste commands into the terminal if the need arises.
There’s already a thousand comments, but I’ll give my opinion anyway. Debian is by far the most reliable distro I have ever used. It’s easier to install than arch in my opinion, and is completely rock solid. However, if you have at least a year experience with linux and you like tinkering, nothing beats arch. I don’t recommend using distros like pop_os, endevour os, or manjaro, simply because once you have a bit of experience, it just introduces more points of failure.
TLDR;Debian, or if you are experienced, arch.
Building off of that:
I recently discovered PikaOS, which is a Debian based distro that… more or less is as Nobara is to Fedora, highly streamlined, tons of optimizations for gaming built in, closer to, but not literally bleeding edge to keep up with driver optimizations, as well as comes pre packaged with a number of common, useful apps and packages.
I have seen some benchmark videos of it actually outperforming Nobara in gaming performance on older hardware… maybe not as old as OP’s, but like, 10% to 20% more frames.
Downsides for this use case, seemingly a relative linux noobie, are that… well its still arguably in the experimental/development phase, it is fairly new, and of course, as compared to something like Bazzite, it doesn’t come with guardrails via sandboxxing everything into flatpaks and making it more difficult to do something destructive to the core OS.