The screenshot with shows no button when no user is listed sounds like a valid bug, it should allow to unlock/add the user as stated in the screen, could you report that upstream on https://gitlab.gnome.org/GNOME/gnome-control-center/issues ?
The screenshot with shows no button when no user is listed sounds like a valid bug, it should allow to unlock/add the user as stated in the screen, could you report that upstream on https:/ /gitlab. gnome.org/ GNOME/gnome- control- center/ issues ?