I gave up on this approach. Instead I mounted a drive to the music files and installed plain MPD with CYP on there. I still use DLNA on all the other devices in the house. This particular machine is just headless so the need for a web client instead of a DLNA client lets me control the music on it.
if upmpdcli is installed and running on the mopidy machine and Mopidy-dLeyna Extension ist installed and enabled, any client should see a DLNA libray with all DLNA servers in your network. NETWORK is here another challenge. this works only, if all machines are running in the same subnet. My Twonky DLNA servers run in a container with own subnet, which makes access difficult - this is why I also changed my plans and mount the audio files into the Mopidy media dir.