The “X server” is what is run on the graphic desktop environment. This is either your Ubuntu desktop host, Windows, or Mac. … With this X11 communication channel properly established via ssh, a graphical applications run on the “X client” will be tunnel across and displayed on the GUI desktop.

Does Ubuntu use X11 or Wayland?

The default Ubuntu means it will be using Wayland while Ubuntu on Xorg obviously means it will use Xorg. You can select Ubuntu on Xorg to use Xorg here. Similarly, you can switch back to Wayland when you feel like it.

Does Linux use X11?

X11 is the graphical environment for most Unix or Unix-like systems, including *BSD and GNU/Linux; it provides access to screen, keyboard, and mouse. X11 is the Unix and Linux graphics drivers.