Try to create a WebHook that triggers a command to the Dgraph instance via EXEC (docker). Making it back up to the local volume - Share this volume with some other instance of your preference for your strategy. Hence, by continuing the webhook script (Bash), by having a positive Backup result you would schedule the script to copy and send via Tunnel that file generated by Dgraph.
That’s one idea only.
I had an idea that could be useful in this case yours if it were implemented.