If you get:
Gtk-Message: Failed to load module "globalmenu-gtk"
every time you launch an app, you have left a Gnome Shell module, which is no longer present on your system, in your
GTK_MODULES environment variable. In my case, I enabled the Global Menu extension in Gnome Tweak Tool and then uninstalled Gnome Shell. To fix, I
/etc/profile.d/globalmenu.sh file and rebooted.