What does HackerNews think of borg?
Deduplicating archiver with compression and authenticated encryption.
Language:
Python
Python source code? Yes, it is on https://github.com/borgbackup/borg (if that was the question).
No cloud? Indeed, borg does not integrate cloud functionality.
You'll either need a directory or a server with ssh and borg to store your backups into. Some people use rclone to clone their borg repos to the cloud.
I highly recommend Borg Backup. I had to give up on Duplicati years ago, perhaps they're OK now. But Borg is magic.
> only something like a file-system+compression could do that
borg handles this just fine. I put all kinds of stuff into borg repositories: raw MySQL/PostgreSQL data directories, tar archives (both compressed and uncompressed), or just / recursively. You can do stuff like:
$ tar -caf - / | borg create …
$ borg create … rsync.net has a special pricing tier for Borg users that might be worth looking into.