Install xss-lock by entering the following commands in the terminal:
sudo apt update sudo apt install xss-lock
Description:
invoke external screen lock in response to XScreenSaver events
Utility to listen for XScreenSaver (XSS) and login manager events and call out to an external screen locker in order to lock the screen.
Homepage: https://bitbucket.org/raymonad/xss-lock
Version: 0.3.0-4
Section: universe/x11