iTunes Sever on Synology NAS and Apple Music
The current release version of the iTunes server for Synology is not compatible with Catalina. If you register a ticket with Synology outlining your problem, they will send you an updated server spk to install.

Having said that, there is still a problem which I'm having and I've not been able to find out so far if it's just me or not. The problem I'm seeing is that albums with multiple artists are being listed in the albums list multiple times. once per artist. A real pain for collections.