SuperTuxKart, one of the golden oldies when it comes to free and open source gaming has a new release out with SuperTuxKart 1.3 improving lots.
To help with performance STK now has the ability for you to change the rendering resolution scaling to get a performance boost, although it does reduce the image quality. There's a few unused graphical effects removed, the texture code was improved, improved screen space reflection and more graphics updates.
Other additions include server bookmarks, gamepad force feedback, loading of tracks with "many checklines" was optimised, custom skidding sounds for karts is possible now and there's also a highscore screen. Lots of UI improvements too like clickable URLs in text, visual and sound feedback when a timed challenge or game is about to end and much more.
See the announcement.