This Docker image can be used to perform backups using duplicity without encryption. This might be useful if you want to perform backups to a trusted location but still get the incremental backups in tar format.
To back up /data to /backup, use the following command:
docker run --rm --net=host \
-v /duplicity-cache:/root/.cache/duplicity \
-v /data:/source:ro \
-v /backup:/target \
tgpfeiffer/duplicity \
duplicity --no-encryption /source file:///target
Note: It is necessary to use --net=host (or fix the --hostname of the container) to avoid the "Fatal Error: Backup source host has changed" error from duplicity.