Follow Instructions At:
https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-vnc-on-ubuntu-20-04
But set the .vnc/xstartup file to be:
#!/bin/bash
xrdb $HOME/.Xresources
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
dbus-launch startxfce4 &
~
~
~
~