IIRC, I have tried this before and it has not worked in the past. The devices are unable to reach the DNS via the tunnel, not sure why. I think you will notice that if you use some other public DNS, that works... I will investigate this at some point.
mh...seems to be a firewall problem. When I allow "any IP" (TCP and UDP) on Hetzner-Firewall it works flawlessly... adding the Cloudron IP to the firewall doesn't work....Any idea anybody?