I’ve read your outline: Synchronization | Kopia
But I’m one of those fools who benefits from seeing specific examples of commands in use. Preferably tested examples.
So an expansion of this page with examples of various targets such as local disk, SMB storage, SFTP, Amazon S3 would be very useful.
Also requesting simple FTP access again 
It’s fine for LAN use…especially when the data is already encrypted.