Anything less than mainline support is ewaste imo. Look how terrible the pi graphics support used to be but now thanks to excellent upstream kernel/Mesa drivers it’s great and will continue to work/improve for the foreseeable future.
The gap between “nothing has been done for this task” and “multiple developers have written, reviewed, and discussed patches for this” is immense and positive.
FWIW i played it on Linux launch week on a 3080, it actually crashed less than on my Windows install. But that’s fair there are a lot of variables that could cause issues.
GTK_THEME is a development env var, it’s not expected to work in many cases. For example GtkSettings:gtk-theme won’t even contain it so apps can be confused.
The post details exactly how it works but yes it’s only about GTK.