Install gnome-screensaver-flags by entering the following commands in the terminal:
sudo apt update sudo apt install gnome-screensaver-flags
Description:
Screensaver for GNOME with flags of the world.
Screensaver contains about 250 static images with flags of the world.
Homepage: http://techblog.zabuchy.net
Version: 0.1-1
Section: universe/gnome