There have been a fair number of requests to backport duplicity 0.8 series to Xenial. Good news, it passes all the tests on Xenial under its Python 3.5. Bad news is that I can't make a PPA entry for Xenial since it requires python3-pytest-runner to run the tests for Launchpad Builder. This is because Launchpad blocks access to anything other than Ubuntu repositories. As usual, all of this is solved using pip3 to load requirements. [pip is to Python as CPAN is to Perl].
I've enabled Python 3.5 in setup, so duplicity will install under pip3:
$ sudo pip3 install duplicity
Snap works as always:
$ sudo snap install duplicity --classic
I am working on the Launchpad issue above. I'll get there!
...Ken