Posted in order to provide the answer.
I have a good experience with LXQt desktop environment installed on top of Kubuntu 18.04, but it still has some odd features - about which it is not that easy as for other desktops to gather information on the internet.
When waking from suspend an odd message appears saying "xscreensaver not installed or not working" - and I cannot get rid of it (I can dismiss it but it comes back next time).
Installing xscreensaver, it locks the screen and asks for password when waking the system from sleep state.
How to stop screen-locking upon suspend?