lightdm does not greet or present login prompt when resuming from laptop suspend

[Connor Kuehl]

Expected result: when opening laptop lid the lock screen presents itself so I can unlock my session

Actual result: the contents of my desktop are visible (windows, etc) and I can move my mouse cursor around but I cannot interact with the desktop session at all. Hovering over UI elements or clicking them has no effect.

In order to get the login prompt I have to ctrl+alt+f1, login at the console, and run sudo systemctl restart lightdm, then I can login normally and resume whatever I was doing from before I closed the laptop lid.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: lightdm 1.30.0-0ubuntu1
ProcVersionSignature: Ubuntu 5.3.0-23.25-generic 5.3.7
Uname: Linux 5.3.0-23-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
CurrentDesktop: XFCE
Date: Sat Nov 23 09:08:32 2019
InstallationDate: Installed on 2019-11-09 (14 days ago)
InstallationMedia: Xubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Elliot (cheese-e-boi)]

Happens with the Dell XPS 9570 (Intel-Nvidia) as well on a fresh install.

[pigs-on-the-swim (dw1-4)]

I experience the same. With XFCE4-Ubuntu 18.04, 18.10, 20.04 (all, no difference). I removed light-locker completely - no difference.
In situations where time triggers locking the unlock screen sometimes appears.
Closing the lid there is the problem described in the bug report above.
Workaround: After opening the lid I type my password into the void and sesame opens the door!
Recap: xfce4-screensaver actually uses the lock screen when closing the lid but does not show it. 100% reproducible.

[Vasco (vasco-visser)]

I am also affected by this bug on xubuntu 19.10. One thing I noticed is that there are two xfce4-screensaver-dialog processes when waking up from suspending by closing the lid. When waking up after suspending via other ways there is only one such process and things work properly.

[Tim Nolte (tim-nolte)]

This is still present with Ubuntu 20.04 and the latest XFCE & LightDM. This is a major pain almost to the point of me wanting to switch back to GDM & Gnome.

[Dmitry Petukhov (hellodima)]

I have this issue too. I'm using Dell latitude 5501, Xubuntu 20 and Xfce. It's very painful.
Is anybody have found the solution?