Cannot lock screen in lxqt desktop

[Reza Housseini]

Hi Guixers

When I click "Lock Screen" in the desktop menu I get a popup with the 
warning

  Failed to run "xdg-screensaver lock". Ensure you have a 
locker/screensaver compatible with xdg-screensaver installed and running.

I tried installing xlock and slock and setting up a screen locker 
service [1] with no success.

Was anyone successfull running a screen locker in lxqt? And why does 
this not work out of the box like in GNOME?

Thanks for your help!

Best,
Reza

[1] screen-locker-service-type