Granvir brings solo and online co-op to mech-building, with Linux support it's officially available today and it's great. They also previously released Granvir: Zero Front, a standalone cut-down version for you to try for free to get a feel for it.
More about it: pilot your Granvir and manage your campaign between battles to find the best equipment and stay supplied while fighting back against the Millennium Company invasion of Inheritance in single-player or with friends in multiplayer co-op. You can end up building some pretty fun mechs in it, a bit of a dream for fans of things like Gundam.

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Game Highlights:
- Equip An Arsenal Of Deadly Weapons: Don devastating melee weapons such as swords, rocket spears, and jaw arms. In addition you can wield powerful long range guns like cannons, machine guns, flamethrowers and rockets. Mix and match them to suit your play style.
- Build Your Granvir Your Way: Mix arms, legs, armatures, and special modules to customize your mech. Defeating ace pilots grants their unique parts for your use.
- Deploy With Friends: Complete any campaign in single-player or multiplayer co-op with up to 10 Granvir pilots at a time. Share parts and resources utilizing the squad depot in rest areas as you plan your next moves.
- Direct The Campaign: No campaign is the same as you manage time, resources, and your route to each objective. Each zone dictates what services and resources are available to you. Use down time between missions to refit and upgrade your Granvir to prevail.
A whole bunch of content is also planned post-release including a new story campaign, new mission environments, more parts for your mechs, new enemies and much more.
I played quite a lot of Granvir: Zero Front and really enjoyed the mech building in it. Really pleases my brain to see more mech games appearing lately that are actually good. Still nice to see games releasing with direct Native Linux support too, hopefully it continues working well.