Good news. The latest version of BTSync actually lets me specify which folder on my Android tablet I want to sync.
That means I can explicitly tell it to sync. the OWL directory that OWLdroid uses by default. (Somewhere between updates of Android and BTSync last year, this facility got lost.)
So it’s looking like BTSyncing between my tablet and laptop are working again. So OWLdroid is a viable piece of software again. (The syncing with the laptop makes a huge difference in day-to-day usefulness.)
Yes, I know this isn’t great. I need to figure out how to ensure that OWLdroid works. The longer term plan is to move to having remoteStorage.js as an option. But that’s a little way down my todo-queue.