Last Epoch, a very promising Action RPG that was funded on Kickstarter already supports Linux, and my recent interactions with their team have been great.
Here's a curious one. Evolvation, a space combat sim from HyperReuts originally supported Linux last year and after going through a revamp Linux support was removed. It's coming back though, as the developer has confirmed.
Jumpai is an interesting one, a platformer for those who have a creative side as the built-in world editor allows you to construct and play your own levels as well as those created by others.
Feudal Alloy is certainly a unique theme, with you controlling medieval robots as a fish. The developer has now confirmed it's releasing with Linux support this month.
TerraTech is one of the more interesting sandbox games I played last year, an open-world giving you a lot of freedom to explore and destroy while you create your own vehicles.
Volcanoids, the game where you build a base onboard a massive steampunk-like moving drill is coming to Linux and the latest update sounds very positive.
Coming to Linux sometime this year, The End of the Sun is a first-person exploration and adventure game set in the world of Slavic rites, beliefs, legends and their everyday life. The developers recently showed some behind the scenes development information.