Whilst searching for a "lock-screen" possibility I stumbled upon "slock" (in suckless-tools package) and "i3lock" (which is it's own package). Where the latter is IMO opinion an elegant solution.
Other than that: One can always have the "screen-lock" button or key-combo activate "dm-tool switch-to greeter" which doesn't really lock your machine, just your session (as do the two other lockers too) ..... that would require exra tweaking of X and the access to the virtual consoles.
"dm-tool lock" really locks the whole machine but isn't very friendly in it's response when wanting to unlock. It's very effective though.