I hadn't have much luck at finding game on linux similar to Sins of Solar Empire: Rebellion (works well with proton). Then digging deeper i've found in my ubuntu repo:
- Endless Sky (Single player. Available on Steam as well. Open Source. Free)
- FreeOrion (more close to SoSE:R, inspired by Master Of Orion, LAN and Multiplayer, Open Source, Free, more complex than Endless Sky)
Great tune, makes my mind time-travel...
Linux Geeks doing what Linux Geeks do..