Thanks much for your reply.
I have 1.7 working nicely now.
After learning more, I agree, there's no need for a graphical greeter screen. That was too many years of Windows experience talking ;-)
I'm posting here recipe that worked for me, in case it is helpful to others. I'm sure that for someone more experienced, not all of this will be necessary:
Disable Wayland and use x.org
Install LightDM in place of GDM to handle logins
Install Mate desktop in place of Gnome
Edit ~/.vnc/Xstartup to run mate-session, the full contents being:
vncconfig -nowin &
exec dbus-launch mate-session