Glad you are happy with Dropbox.
For future readers of this thread, best to understand that Bonjour is not Local Sync. They are two different sync methods, as fully explained in the “DEVONthink Manual”.
Bonjour is one of three sync methods I use (others being local NAS WebDav and Dropbox as the only cloud-based method) with no issues.
See the post Syncing on the local network: How do I add a Local Sync Store on the iPad? - #3 by halloleo which coincidently landed today.