I did manage to get the phone unlocked, having tried various Recovery options. But the /e/ OS installer still did not finish.
Then I took the hints above and used the method at the Command line option shown on the page from the link Install /e/OS on a Nothing Nothing CMF Phone 1 - “tetris” .
This method was really easy and quick to follow. I really do not think that I am an advanced user at all, but I can follow the steps as shown, and /e/ OS was installed in 10 minutes.
With thanks for the support and hints. That is what community is for.