1: You can login and not start up a display (e.g. when you SSH into a box). The login manager is seperate from the display manager. You don't necessarily have t

1: You can login and not start up a display (e.g. when you SSH into a box). The login manager is seperate from the display manager. You don't necessarily have to have a display attached. 2: The display manager starts up a window manager, which figures out where to draw your apps. X11 or Wayland is the underlying tech that KDE, Gnome, etc, uses to manage displays/windows. Ly draws straight to the terminal, which I'm pretty sure is faster. And it allows some flexibility when running multiple window managers. I've found having multiple window managers installed can be a little unstable. SDDM didn't like it, but it works pretty good with Ly.