Comment # 11 on bug 1123424 from Stefan Hundhammer

Notice that this "Clean Up" is a pop-up menu from the same menu bar where you
can see "File", "Edit", "View", "Go To", "Treemap". The font is tiny (probably
some last-ditch minimum size as a fallback when all else fails), but the icons
are there since they are compiled into the application via Qt resources. The
"Clean Up" menu title might actually be a window manager decoration (or
whatever the Wayland counterpart of that is called); that might be why it is
rendered correctly.