A new game I discovered that has a parallel Linux release is "Starsector" formerly know as "Starfarer" in it, you take on the role of a fleet commander flying the space lanes and shooting things.

From what I can tell, you will also be able to carve out a name for yourself as a trader. From what I've played so far, it really reminds me of Mount and Blade - you build up a fleet and attack roving bands of pirates across the map; when you do, you are taken to a battlefield where you can give orders 
to your fleet ships - in the larger battles, you have arbitrary objectives, but killing off or routing the enemy is the main focus.

I really like the detail and you can swap mods on your ship, level up your crew members - and in future hire officers to help improve your ships prowess.

I've made a quick video to demonstrate the early game and it is actually really fun, although you do really need to pick your battles better than I do.

Also, the video is the first to include a new intro and outro sequence I'm trying (let me know if you like it or not).