Install x2go server in Debian 9

Add repo

vi /etc/apt/sources.list.d/x2go.list

Add

deb http://packages.x2go.org/debian stretch extras main
deb-src http://packages.x2go.org/debian stretch extras main

Add key

apt-key adv --recv-keys --keyserver keys.gnupg.net E1F958385BFE2B6E

Install X2Go server with

apt-get update
apt-get install x2goserver x2goserver-xsession -y

Now you need to install one of the Desktop, it is better use XFCE on remote servers.

apt -y install xfce4