I mean, I can basically advise the same list as I do for anybody.
- Mindustry
- OpenTTD
- Luanti (especially MT-Game, I actually dislike MineClonia)
- Endless Sky
- Shattered Pixel Dungeon
- FreeCiv
- YGO Omega & EDOPro
If you're open to buying and/or piracy, I can also suggest the following:
- OpenRCT2 (get both RCT Deluxe and RCT2)
- OpenXCom (get both X-COM: UFO Defense and Terror From the Deep)
- CorsixTH (Theme Hospital)
If you're okay with more violent games, any Doom sourceport (like GZDoom) with FreeDoom phases 1 & 2. There's also OpenQuake, but I don't do 3D much.