libnx-x11-dev - 2:3.5.99.19-3+deb10u2 main

NX is a software suite which implements very efficient
compression of the X11 protocol. This increases performance when
using X applications over a network, especially a slow one.
.
This package provides development headers of the libNX_X11 library (a
libX11 drop-in replacement used by nxagent).