Based on their list of supported procotols[0] you should be able to make rclone work. Worst case you can use the SFTP backend.
I would also recommend adding `sha1sum_command = /usr/bin/sha1sum` to the rclone.conf entry in order to enable rclone cryptcheck.
[1]: https://docs.hetzner.com/robot/storage-box/access/access-ssh...