The documentation says
The nymea system needs to be configured to connect to nymea:cloud and wait for incoming connections from nymea:app. In order to do so, go to System Settings → Cloud.
I can not find a Cloud entry in System Settings. (My GUI is in German, but I see not even a similar entry)
Oh. That documentation is outdated. Can you paste the link please?
Instead, nowadays, you simply enable the remote connection in system settings → connection settings. No cloud account or anything needed. Just make sure your user passwords on nymea are strong enough so they can’t be guessed.
Oh my, it’s fast. It’s also very elegantly done. I like it.