OpenTTD - amazing reviews for the free game from 14 Mar, 2004.
Dwarf Fortress - bought it, I have not played it yet, though. I know it got Linux port not so long ago.
Minecraft - I know this childhood gem, but I hate to have a Microsoft account on Linux and I know there are some launchers. Still hate to play for me single-player game with an account.
Dwarf Fortress is quite the rabbit hole. It's so much more than just a game. The complexity of the simulation has actually made me wonder about simulation theory IRL.
For DF: The free version had a Linux build for a long time. The paid version adds new graphics, and it took a while for that to get a Linux release.
For Minecraft: you should be able to play without an account if you're single player and using a third party launcher. I almost exclusively play with friends.