https://store.steampowered.com/app/2645580/Free_Stars_The_UrQuan_Masters/

Hands down. One of my favorite games of all time, an open world, hilarious, fun, sprawling adventure with music that slaps SO hard. Originally titled Star Control 2, went through some crazy copyright hell but now is getting an official sequel soon, over 30 years later.

EDIT: Oh wait, you said Linux. I think it works on Steam Deck and Proton though, does that count?