I am interested in using Joplin Cloud and I know that there is a free trial period available. However, I do not want to create an account (including providing payment details) just to find out that the interface language cannot be changed to German. Could you please confirm if the Joplin Cloud interface can be set to German?
I don´t use Joplin Cloud either, but I do self host Joplin Server.
In my experience once I´ve created the necessary user accounts on the server and activated syncing there is really no need for logging into the server anymore. It is "set up and forget".
Joplin Cloud has more functions than Joplin Server but I guess that everything is used from the Joplin client.
Short version:
In my opinion it does not matter if Joplin Cloud is only available in English. Users won´t notice since all the functions are accessed via Joplin client