Any thoughts on supporting ProxyJump for SFTP backend?
The main use case is that remote sftp storage machines, behind a firewall, would usually create a tunnel to an intermediary. In order for rclone to connect through the intermediary first, the ProxyJump would specify the intermediary (often as a name to another SSH server listed in ~/.ssh/config, or in rclone.conf).
As a slightly related side feature: It may be nice for rclone to support looking up sftp clients in ~/.ssh/config, to save having to list them twice for those who want both SSH access to a remote, and to use SFTP for rclone backups from/to that remote. Although I'm not quite sure the syntax to be used to indicate such in rclone.conf.