To be able to listen to all signals using the glib-bindings it would be nice to have the same abilities as the python-bindings dbus.connection.SignalMatch.
New code should use GDBus, where g_dbus_connection_signal_subscribe provides this. Legacy dbus-glib code can drop into libdbus and use dbus_connection_add_filter if you're sufficiently masochistic. We're only supporting dbus-glib for backwards compatibility at this point, so I think this is now WONTFIX.
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.