Clone Drone in the Danger Zone from Doborog Games seems like a rather fun third person sword fighter and the developer has made adjustments for Steam Play.
The newer team behind Planetary Annihilation: TITANS has put out two new test builds, one built with newer modern tools and the other on their legacy toolchain. It comes packed with new features and updates too.
While there's a lot of good games available natively for Linux, one area we really are lacking in is games for a younger audience. Steam Play has helped a lot here!
I've been excited to try out Hypergate for a while, as a long time Freespace fan I'm always itching to play more space combat games. It's now officially out, with Linux support.
GoNNER is a randomly generated action platformer with 'roguelike elements' from developer Art in Heart and publisher Raw Fury that leaves a lasting impression.
Space Haven from developer Bugbyte Ltd (Battlevoid: Harbinger) looks like a very interesting colony building sim with a difference. Your colony is a moving spaceship!