Honestly, you’re not going to have a lot of luck with recent games. The sandybridge i5’s were great back in the day but their time has come. I had a 2600 for a looong time but it’s been out to pasture for a couple years now.

Check out the “patientgamers” communities, they like to play older games that would run a lot smoother on your hardware.

Into the Breach is a fun game. Command and Conquer 3 and you could get into emulation like Smash bros or Mario Kart.

With that kind of hardware, nothing you could tweak would help a whole lot.

You need an upgrade mate.

Something like Slay the Spire should be easy to run, essential roguelike deckbuilder

I agree with the other posters, your hardware is going to hold you back. But you could try switching to a lighter desktop environment like LXDE instead of GNOME. This user found a small increase in performance: https://www.reddit.com/r/linux_gaming/comments/dg87jp/does_the_desktop_environment_matter_for_gaming/

But they had somewhat beefy hardware. If you’re truly at the limit of your specs, 100% CPU/RAM usage, your performance increase could be even more.