I don't know what fixed it, but I kept the machine up-to-date and the current versions are:
deja-dup 38.0-1ubuntu0.1 duplicity 0.7.17-0ubuntu2
And with these versions, backups now work again as expected.
I don't know what fixed it, but I kept the machine up-to-date and the current versions are:
deja-dup 38.0-1ubuntu0.1
duplicity 0.7.17-0ubuntu2
And with these versions, backups now work again as expected.