The xdg-shell protocol is a sort of core desktop protocol. It has an opinion about everyone's favorite Wayland topic (server-side decorations), and if you have

The xdg-shell protocol is a sort of core desktop protocol. It has an opinion about everyone's favorite Wayland topic (server-side decorations), and if you have a different opinion, you need to use the xdg-decoration-unstable-v1 (as it still seems to be called) protocol. Fortunately, it seems like the Wayland desktop scene is converging on that one now. There are still some missing pieces, but the situation isn't disastrous anymore.