I have a headless Ubuntu PC running 18.04.1 Desktop. If I plug a monitor into it, Vino starts automatically and I can VNC into the box. I did set the "Sharing" item in the control panel to share the screen.
I followed the instructions at How to use Ubuntu 18.04 on VNC without display attached? to install the dummy monitor.
If I ssh into the box and manually start Vino with
then it works fine and I can VNC. How can I make it work without needing to do this?