Package: gdm3
Version: 3.22.3-3+deb9u1
Followup-For: Bug #891599
This actually looks like it might be a bug in gnome-shell, and still present
in 3.28. This silly-looking(?) bit of logic is present there in
js/ui/status/network.js:
_sessionUpdated() {
let sensitive = !Main.sessionMode.isLocked &&
!Main.sessionMode.isGreeter;
this.menu.setSensitive(sensitive);
},
I.e. it looks like it's hard coding things to not allow interaction from the
greeter, no matter what permissions you might or might not have set.