libx11-doc 2:1.8.4-2ubuntu1 (arm64 binary) in ubuntu mantic

 This package provides a client interface to the X Window System, otherwise
 known as 'Xlib'. It provides a complete API for the basic functions of the
 window system.
 .
 This package contains supplemental documentation for the library found in
 libx11-6. Non-developers likely have little use for this package.
 .
 More information about X.Org can be found at:
 <URL:https://www.X.org>
 .
 This module can be found at
 https://gitlab.freedesktop.org/xorg/lib/libX11