Confirming the usefulness of the upstream bug post. The easiest workaround is to unset the UBUNTU_MENUPROXY environment variable. Should you want that state of affairs to be semi-permanent, the variable is set in two files:
/etc/X11/Xsession.d/80appmenu
/etc/X11/Xsession.d/80appmenu-gtk3
Comment out the contents of those files and gnome-terminal's menu will behave properly. We can also assume you'll need to reset the variable should you be gripped by the need to suffer Unity and the Mac menu.
Confirming the usefulness of the upstream bug post. The easiest workaround is to unset the UBUNTU_MENUPROXY environment variable. Should you want that state of affairs to be semi-permanent, the variable is set in two files: Xsession. d/80appmenu Xsession. d/80appmenu- gtk3
/etc/X11/
/etc/X11/
Comment out the contents of those files and gnome-terminal's menu will behave properly. We can also assume you'll need to reset the variable should you be gripped by the need to suffer Unity and the Mac menu.