At the moment I use WebDav as sync target, but I backup local and on the server.
The advantage of the local backup via JEX is that I can also import the data into another Joplin instance to extract only one note.
I only have the server backup in case there is a total loss of the server and I need to restore everything.
But I think with the Joplin server the backup of the server will become important with the time, because here also the shared notebooks are stored and the infos of the individually shared notebooks.