Tecadmin published a tutorial about installing LightDM on Ubuntu Desktop.
Installing LightDM on Ubuntu Desktop
LightDM is a free, opensource and lightweight X Display Manager for Linux Desktop systems. It is also used as a cross-desktop display manager. It supports various Desktop environments including various display technology, such as Wayland, Mir, and X windowing systems. This tutorial will help you to install the LightDM display manager on the Ubuntu Desktop