Gents:
Thanks for all the email feedback. The consensus appears to be that switching from Ubuntu/mate-desktop to XXX-Mate OS_version produces no quick advantage and may in fact be a regression. For a practical, risk-adverse guy like me with 2 supported years remaining on Ubuntu 16.04.5 I take the message clear. The previous failure of my UBUNTU upgrade 16.04 —> 18.04 then simply advises I take the milk-cow route and never risk upgrade on well-working computer appliances. When I do update GPU from NV-660 to NV-1060 the drivers will be there.