Crayon If we are talking Linux gamedev there are 2 main engines I like:
Godot - mature, stable, plenty of features. Scene structure is really powerful and nice to work with.
Armory3D - Tight Blender integration, visual scripting very similar to Unreal Blueprints, Haxe is a pretty great programming language, super cross platform, unfortunately a lot less stable than Godot right now (it's only on version 0.5 so that shouldn't be surprising), and the frankensteined Blender/Gamedev workflow can feel really weird.
I don't consider Godot to be behind Unity. Not significantly so anyway. The community is a bit smaller, the 3D performance is very slightly worse but improving, and there are not as many existing examples to work from (but still quite a lot!), on the other hand scenes are better than prefabs, its 2D tools are amazing, and the cross platform editor is better. If the last time you tried it was a couple of years ago you probably tried it back in the 2.x era, Godot 3 changed a lot and it has been improving rapidly since.
For tools, Blender and Krita are amazing. Gimp also works for some quick texture work but I don't think it's that great. The Substance suite (not FOSS) runs on Linux (painter, designer), and there's ArmorPaint improving rapidly if you are worried about Substance Painter going away now they are owned by Adobe or want a FOSS alternative.
If you want to do pixel art, you've also got Aseprite and a few others.
IMO, it's totally doable to be a Linux gamedev.
EDIT:
As an extra, I just want to point out that I've donated to both Godot Engine and Armory3D. I donate more to Armory3D now because I really want it to improve. I'm really happy that Godot has grown, as I think having good FOSS solutions for gamedev is really important. Armory3D also had an awful experience with Patreon, where they were getting around $1600 a month and then Patreon just wiped their account because of a case of mistaken identity, said "oops we made a mistake too bad, but we can't undo it. Feel free to start a new Patreon from scratch.". I felt super bad for them. They now raise their money by selling builds on Gumroad:
https://armory3d.org/fund.html and are back to earning something near what they were earning before. Everything is still FOSS (zlib license).