Ok, I have to say here that Lisa has been the shining jewel here. And I just got bunted from the Private Message system, having ‘sent more than I’m allowed in 24 hours’— hmm.
So I will just have to put the appreciation here.
She found the problem - a slightly ‘leftover’ .htaccess file I had put in the system folder.
...never in a million years…it was very hidden.
Once ‘nuked’, as she put it, I could update successfully, with no database errors.
This went very smoothly, but then the site had only white screen to show. This is because I didn’t realize to remove the Pages things from our friend before upgrading.
Since upgrade is really simple, especially direct on a Unix system, I’m just going to put back the original site one more time from backups, _remove_ Pages from our nice friend, and then upgrade again. That part will take about 5 minutes.
That’s what I’m doing, then.
Birds sing in the trees in the courtyard, or tweet anyway, as the light is here.
Thank you, Lisa. Really appreciated, and the experience of your professionalism there.
Take care, and make up your own rest debt, please 
with nice thoughts, from Basel on the Rhine,
Clive