On Thursday 03 September 2020 14:56:01 deloptes wrote:
> Dr. Nikolaus Klepp wrote:
> > Remove or comment out all lines except these 2, then reboot:
> >
> > auto lo
> > iface lo inet loopback
>
> good catch Dr. Klepp - I have completely forgotton that there are still
> people on desktops with entries in the file.
> When I read your question it lighted up again - to manage the networks by
> NetworkManager there should be no entries in there (except lo as pointed by
> you)
>
>
>

Changed these lines now (contrary to all advice found by online "experts"!), 
and I am now rebooting in order to do a test run. 

Science means that I ought to be able to reproduce your results, rather than 
attributing my problems to the Men in Black. 

Bill