Are apps on one Linux desktop environment compatible with another desktop environment? My distribution is Arch, and I am using Plasma 5 DE. When I install and run apps that are said to be built for another DE such as Gnome or pantheon, the apps run but the GUI seemed a bit messed up. For example, the panteon mail application lack the top system menu (which allows you to drag, close, or minimize the window) and Nylas N1 mail application's top system menu shows
X11 rather than the normal KDE style menu.
I understand that many apps with GUI are based on GTK+, Qt, or Electron nowadays. But to me, it seemed like they are all compatible to X11 and there is no reason why these apps do not function properly on another DE based on X11.