bug reporting documentation mentions bugzilla, not gitlab
My understanding is that bugs in gtk+ should be reported via gitlab and no longer via bugzilla. (Bugzilla told me that if I don't find the component there I should go to gitlab.)
Yet when I search "gtk report bug" on Google the first result is this: https://developer.gnome.org/gtk3/stable/gtk-resources.html
And this talks about Bugzilla. Should be updated.