Hello. I released a new version of my theme changing app for Linux.
It adds the feature to (force) set the theme of gnome libadwaita apps without libadwaita patches, among other minor tweaks. Besides that, it can change GTK2/3/4, Kvantum, icon and cursor themes, GTK CSS and some appearance settings across GUI frameworks.
Hope this is useful.
yes it works on all desktop environments.
gtk4 themes are similar to the gtk3 ones - it’s still css, maybe with some addidtions