Hi Richard,
to make a long story short : when the very first document describing RTP-MIDI was published (RFC4695), it appeared that it was too “generic”, as it was made of 3 parts, one of them being mandatory to implement, the two others being optional.
So Apple decided to implement the protocol using only the mandatory part, and replacing the session control part by its own protocol, described in the Apple’s Developer docs (with some errors…). And this documentation just specifies the name to be used by mDNS (alias Bonjour), with absolutely no details about the expected structure…
By the way, this situation also led to some weird situations where two companies had a different understanding of the way the protocol should be implemented… (like one was using “stricto-sensu” the RFC4695 document, and the other was cloning the Apple way of session handling)
Now, back to your problem : don’t worry about Bonjour. It just publishes on the network the IP address used by RTP-MIDI devices, along with their port. The Zynthian RTP-MIDI daemon simply ignores this, and throws away all mDNS messages with RTP-MIDI information. And the Zynthian does not even publish these informations (at least from the daemon I wrote, maybe other guys in the team have added it)
From the peer computer, using the RTP-MIDI control panel, just create a manual entry in the directory (click on “+”, then enter the IP address of the Zynthian, along with port number 5004, and give your directory entry a name). Once this entry is created, just associate it with a session (which is nothing than a MIDI port for your Mac) and click on Connect button. The Mac will then connect to the Zynthian as a session initiator and it will work