There are multiple options both stable and latest:
The pip3 stable install will be delayed until I resolve a problem on pypi. Use latest for now.
Note 1: UNINSTALL duplicity first if it was installed from a different source.
Note 2: Launchpad PPAs contain builds for Bionic 18.04, Focal 20.04, Hirsute 20.10, Impish 21.04, and Jammy 21.10.
Note 3: Xenial 16.04 works with Snap and Pip installs, but cannot be built under Launchpad PPAs at the moment.