Thanks, Daniel, for those pointers. Here’s what I ended up doing:
opened “Settings”, “Region & Language”
clicked on the “+” below “Input Sources”
clicked on the three dots to expand the list (since there are a number of flavo(u)rs of English installed)
scrolled down to “Other” and clicked on it
The first time I got to this point, Settings froze up and I had to terminate it and start over. The second time it worked, bringing up a long list of languages. I typed in “french” and scrolled to the “French (EuroLatin (SIL))” entry.
I clicked on that entry, then the “Add” button in the top right corner of the dialog. The new item was added to “Input Sources”:
and a dropdown selection list was added: