I thought you all should know. Hybrid Backup Sync and Cloud Backup Sync have now been added to the QTS App Center under Beta Lab, as of yesterday, May 30, 2016.
https://www.qnap.com/i/en/app_center/in ... ontent_top
I have not yet tested this yet, but will soon. If you look at the changelog for Cloud Backup Sync (the module that enables sync to cloud backups in Hybrid Backup Sync) now has Amazon Cloud Drive listed as a "New Feature". That means there is official Beta support for sync to Amazon Cloud Drive (once again).
I believe this is the moment we have all been waiting for. Let's try it out!
Lastly, as a side note, they specify that ACD support is under the "Sync" ability, not the "Backup" ability. This should help you understand how to configure it.
Woohoo!