Dear x2go team,
according to x2goserver/bin/x2goruncommand xfce4 is being
      launched by executing xfce4-session
    
239   elif [ "$cmd" == "XFCE4" ] || [ "$cmd" == "XFCE" ]; then
      240        cmd="/usr/bin/xfce4-session"
    
According to https://docs.xfce.org/xfce/getting-started startxfce4 should be used to start xfce, at least from command line.
Command linestartxfce4 to start an Xfce
      session or choose Xfce Session from the login
      manager...