in many cases QMenus don't have a transientParent in their QWindow, this breaks in wayland as popups are forced to have a transientParent.
both plasma and QWidget based applications have this problem, but seems to have different causes.
example of qwidget application: konsole has the bookmarks menu and the sessions submenu broken, looking in QWaylandWlShellSurface::setPopup there is no parent.
for plasma, our qmenus are created by qquickwindows(not qwidgets) seem to not have parent either,this seems to be hackable around