Installing VNC is straightforward, until it doesn’t really work as you see a blank grey screen when viewing with VNC Viewer.
Here's how I solved it:
1. Install gnome-session-flashback:
$ sudo apt install gnome-session-flashback
2. Add this to ~/.vnc/xstartup:
#!/bin/sh
autocutsel -fork
xrdb $HOME/.Xresources
xsetroot -solid grey
export XKL_XMODMAP_DISABLE=1
export XDG_CURRENT_DESKTOP="GNOME-Flashback:Unity"
export XDG_MENU_PREFIX="gnome-flashback-"
unset DBUS_SESSION_BUS_ADDRESS
gnome-session --session=gnome-flashback-metacity --disable-acceleration-check --debug &