'Critical Annihilation' [Official Blog, Steam] is a rather fun looking shoot 'em up that features destructible voxels. Linux users asked for a build and the developer has put up a beta.
Honestly, I think this one looks like a crazy amount of fun so I am surprised it has so few players.
The developer put up a Linux build from requests for it, to access it you need to opt into the beta from within Steam. The developer has noted it's not really supported right now, as they have yet to setup a Linux machine, but it's nice to see a developer respond to requests for a Linux build.
It's also in Early Access, so it's still under development as a whole. The reviews even this early on are very positive, so the developer could be onto something here.
It's currently single-player only, but local co-op is currently under development. A game like this is begging for online support.
About the game
Critical Annihilation is a Twin-Stick SHMUP (Shoot-em Up) made entirely out of tiny voxels. We take advantage of voxel technology to hype up the explosive gameplay. Everything is destructible to its core. As your home planet gets invaded by aliens you decide to take up arms with the rest of the planet and annihilate every single alien in site. As you progress in the game you'll bring yourself to whole new planets like the Moon and Mars until you've reached the aliens Mothership. Why exactly are these cliche aliens attacking your cliche planet in the good old fashion cliche way? It's for you to find out as you destroy every cube of their being. This is the same game played by popular youtubers Markiplier and JackSepticEye; Critical Mass. Now with updated art and updated code to bring you a more full, and action packed experience.