I played a lot of FreeCiv and had a lot of fun with it. Not sure if it’s still dev/maintained

They do, but it’s a very small part of their total financing (less than 1% I think), and they don’t have government appointed staff or anything like that.

Are you trying the original or Enhanced Edition? I’ve had no issues playing the EE versions of Infinity Engine games on Ubuntu

This 100%. The only games I’ve managed to finish in the past ten years are on Switch or a portable system.