While setting up a backup using rclone, I encountered problems because I had not initially configured “Rclone local repo”. When using rclone directly, this is not necessary. To prevent other users from encountering the same problem, I suggest adding the following note to the page Rclone Destination after the text ... which will otherwise be set to local, which works for most setups.
Note: You must add a remote called local with the storage type 'Local Disk' to the rclone config for the use of duplicati with rclone.