In the FAQ [1] SSHFS is mentioned a few times and here is the citation where I got this idea from when I read it way back when:
“When Borg is writing to a repo on a locally mounted remote file system, e.g. SSHFS, the Borg client only can do file system operations and has no agent running on the remote side, so every operation needs to go over the network, which is slower.”
SSHFS would be tool agnostic/transparent though of course would result in operations going over the network as it’s not a local repo, but pseudo-local.
I’m curious, how do you use plain SFTP transport with borg using rsync.net?