So, I bought DROX + DLC and I like the game but I don't understand the DLC-thing. I only have one .exe to launch and the title screen says Drox + Invasion of the ancients but I don't see any options to play with or without DLC ?
Is the DLC implemented in the main campaign ? If so, I tend to uninstall it and play Drox operative normal campaign first.

Dlc doesn't change campaign. It adds some things above original game(more ships, items)

Would getting the DLC fix me not seeing ANY ships to start the game with in my Linux version?

I think this is either a bug or something with the installer being incomplete.