After having jumped through all the hoops needed to get the client installed (way to complicated if the goal is to get SSL to everybody. But it’s still in beta so I’m giving it a pass for now) I finally ran into the one thing I can’t fix myself:
There were too many requests of a given type :: Error creating new cert :: Too many certificates already issued for: synology.me
The DDNS domains from synology where added to the publicsuffix list several days ago. Please push them to the validation server so I can finally get the certificates.