Retropie AND LXDE GUI. Second X Session? How?

[derebo]

Hello,

Please, give your views on how to run Retropie (on a Raspberry Pi 3) on my TV set (HDMI) and be able to login remotely from a Windows laptop to an LXDE X session.

If I configure raspi-config to desktop login and Retropie to desktop autologin, TV will show Retropie (great!) but VNC viewer will show a black screen...

pi@raspberrypi:~ $ sudo raspi-config
Removed symlink /etc/systemd/system/default.target.
Created symlink from /etc/systemd/system/default.target to /lib/systemd/system/graphical.target.

raspi-config: DESKTOP autologin
RetroPie-Setup: start Emulation Station at boot

pi@raspberrypi:~ $ sudo systemctl status vncserver-x11-serviced.service
● vncserver-x11-serviced.service - VNC Server in Service Mode daemon
   Loaded: loaded (/usr/lib/systemd/system/vncserver-x11-serviced.service; enabled)
   Active: active (running) since Fri 2017-11-17 11:16:13 CET; 52s ago
 Main PID: 839 (vncserver-x11-s)
   CGroup: /system.slice/vncserver-x11-serviced.service
           ├─839 /usr/bin/vncserver-x11-serviced -fg
           └─865 /usr/bin/vncserver-x11-core -service

Nov 17 11:16:13 raspberrypi systemd[1]: Started VNC Server in Service Mode daemon.
Nov 17 11:16:14 raspberrypi vncserver-x11[865]: ServerManager: Server started
Nov 17 11:16:14 raspberrypi vncserver-x11[865]: ConsoleDisplay: Cannot find a running X server on vt2
Nov 17 11:16:14 raspberrypi vncserver-x11[865]: ConsoleDisplay: Found running X server (pid=872)
Nov 17 11:16:42 raspberrypi vncserver-x11[865]: ConsoleDisplay: Cannot find a running X server on vt1

So VNC server is up and running. And I have managed to display LXDE in the TV set as well by running it from command line with 'startx' so I think it has to do with opening a second X session but how to accomplish it, that I would like to learn about.

FYI,this is my setup:

2017-07-05-raspbian-jessie-lite
sudo apt-get update
sudo apt-get upgrade
sudo reboot

LXDE as GUI
sudo apt-get install --no-install-recommends xserver-xorg
sudo apt-get install --no-install-recommends xinit
sudo apt-get install lxde-core
sudo apt-get install lightdm
sudo reboot

sudo apt-get install realvnc-vnc-server
sudo systemctl start vncserver-x11-serviced.service
sudo systemctl enable vncserver-x11-serviced.service
sudo reboot

At this point I can log in remotely via VNC Viewer and nice LXDE GUI will show. Blank screen shows after installing Retropie:

sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install git
cd
git clone --depth=1 https://github.com/RetroPie/RetroPie-Setup.git
cd RetroPie-Setup
sudo ./retropie_setup.sh

Thank you in advance for your feedback!

[herb_fargus]

@derebo pick one or the other. You can't do both