I had a lot of trouble getting the unity editor working on my steam deck, but that may have been due to using an editor version from 2021 (for unrelated reasons). It seems to behave fine on a normal desktop environment though.
Unreal works okay for me, but I’ve had to submit a few patches upstream to work out some Wayland issues. Other than that, it’s about as bloated/buggy/slow as it is on windows. Most of the time if I think there’s some Linux-specific issue I’ll open the same project on windows only to discover it was the same.
I'm not trying to prematurely optimize but my game worlds are very large, (I have a working to scale earth for example) (oops, forgot to mention, to get good large world behavior, compiling with double precision is a must! (https://godotengine.org/article/emulating-double-precision-g...)) so I've been watching lots of GDC and other talks from AAA titles and how they do their rendering pipelines, and my conclusion is that shaders are really the powerhouse of gamedev these days and anyone interested would do themselves a favor to start learning the quirks of your engines shader language now.