The following should be installed by apt, yum, etc., depending on your OS.

NOTE: Some distro's may have different names for these.

sudo apt-get update 
sudo apt-get install -y \
        build-essential \
        intltool \
        lftp \
        librsync-dev \
        libffi-dev \
        libssl-dev \
        openssl \
        par2 \
        python3-dev \
        python3-pip \
        python3-venv \
        python3 \
        rclone \
        rsync \
        rdiff \
        tzdata

Since Python3.11 site package directories have been marked as Externally Managed and now require using --break-system-packages to install into them. This means that a package like duplicity with many packages must use a virtual environment, or venv, to install their packages. Rather than going through the manual process of producing a venv, activating it, installing duplicity, etc., we will be using pipx from now on to install duplicity. This way we get the same effect as a pip install, but isolated in a venv.

To install follow instructions below. Steps (1) and (2) are important.

PyPA (Python Packaging Authority) has been making rapid changes to the way we install Python modules.
To accomodate installing new packages on older Pythons prior to 3.11, it is necessary to upgrade packaging tools like this:

sudo python3 -m pip install --upgrade pip pipx

NOTE: Failure to upgrade will probably result in a failed install. <--IMPORTANT!

To make sure the pipx dirs are on your path do:

sudo pipx --global ensurepath  # for all users
pipx ensurepath                # for single user

If you have an existing duplicity on your path and it was not installed by setup.py, pip, or pipx, you must uninstall it using the same method by which it was installed.

You can tell if you have multiple instances by doing

which -a duplicity

and then use apt, yum, snap, or other command to remove them.

Chose one of the following depending on whether you want to install for all users or the current user. Use both if needed.

With --global duplicity will be installed in /usr/local/bin/duplicity and its many packages in /opt/pipx/venvs/duplicity.

Without --global duplicity will be installed in ~/.local/bin/duplicity and its many packages in ~/.local/pipx/venvs/duplicity.

sudo pipx --global install duplicity[==version]

pipx install duplicity[==version]

You can keep multiple versions of duplicity by supplying --suffix=version.

sudo pipx --global install --suffix=version duplicity[==version]

pipx install --suffix=version duplicity[==version]

For more information on downloading duplicity's source code from the code repository and developing for duplicity, see README-REPO.

For source docs: http://duplicity.readthedocs.io/

For more information see the duplicity web site at:

http://duplicity.us

or at:

http://duplicity.gitlab.io

or post to the mailing list at:

https://lists.nongnu.org/mailman/listinfo/duplicity-talk

or post a new issue at:

https://gitlab.com/duplicity/duplicity/-/issues