I want LightDM login prompt after system wakes up from suspend

[vrgovinda]

Hi all.
1. I am on Xfce 4.18 in Devuan GNU/Linux. I use LightDM as login manager [should I call it `Display Manager?'].

2. In xfce4-power-manager-settings, under `System' tab, I have checked the option `Lock screen when system is going to sleep.'

3. When `xscreensaver' was installed, after waking up from sleep, I got a faithful prompt asking for my password. 

4. I didn't wish to have `xscreensaver' just for this sake. I wanted to get the LightDM login after the system wakes up [also lightDM can be customized to look pretty too!]. Therefore, I have uninstalled xscreensaver.

5. However, when the system does go to sleep [suspend to RAM], either manually or automatically, I don't get the LightDM login. I assumed that the login manager will be detected automatically. How can I tell Xfce that it should display the LightDM login prompt.

Maybe useful: I have created a launcher in my panel to lock screen and display LightDM prompt when I unlock the screen using `dm-tool lock'.

Thanks.
vrgovinda