I see now, thanks. The lock screen in Unity7 is actually lightdm, not gdm. That's despite the fact that you logged in originally from gdm :)
** Package changed: gdm3 (Ubuntu) => lightdm (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1782101 Title: gdm nonfunctional on active screen switch To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1782101/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs