I’m just a user, but here is my understanding:
Duplicacy is written in golang and hence its’ a self-contained native executable with no dependencies (outside of trivial) on each supported platform. All it needs from the backend to work is file access API with ability to upload, download, rename, and delete – and that’s pretty much it; all work is done on the client. There is no “server” mode functionality, like you might find with Borg. It’s strictly client-side software.
There are however some use cases that may benefit from being able to run another instance of duplicacy client closer to the storage, e.g. on the server – for example deep check with hash verification (that would otherwise result in full download to do rehashing via SFTP; some backends support that via API however), or replication from one storage service to another (to avoid download and re-upload).
Those are however all “nice to have” things and not required for backups to work (and is mostly cloud compute type of deal; it can be done on any other cloud platform that has fast pipe to your storage.)
With that in mind I’m not sure what this
would entail: if you make storage available via one of the supported protocols, (sftp is one of them of course) – duplicacy would work, I don’t see how more explicit that support might be.
What are users asking for specifically? Because your understanding is correct – if SFTP is supported – duplicacy will “just work”