A monitor, TV, or any type of virtual screen or other device meant to project video from the computer is considered a ‘display’ on a Linux system. In some contexts, it may also be referred to as a ‘screen,’ but you get the idea. We can check which displays are connected to Linux using a few different methods. This can help us determine information about detected displays, connected screens, and troubleshoot problems with video not displaying (whether it be physical or over a network).
SDDM (Simple Desktop Display Manager) is a modern, free and open source Display Manager available on Linux and other Unix platforms like FreeBSD. It works both with X11 and Wayland, and is based on QtQuick, a framework to build QML applications. SDDM allows a great degree of customization and; thanks to this, a lot of custom themes are available for it.