It appears that when sending a MIDI message, say a note on or off, via Pd's midiout that this is not passed on (correctly or at all?) via MobMuPlat. A simple test is to create a patch that sends 144, 60 and 100 in succession to the midiout object - this should start a middle C note sounding on an attached MIDI instrument.
What operating system, and what version of the operating system?
What type of midi output target do you intend (virtual port, hardware dongle, etc) and do you have specified in the Audio+Midi settings page, under Midi output?
Confirmed,
Someone asked to force a NoteOff message instead of NoteOn zero velocity and had to use midiout object.
iOS 12 virtual port (didn't test a hardware yet)
It appears that when sending a MIDI message, say a note on or off, via Pd's midiout that this is not passed on (correctly or at all?) via MobMuPlat. A simple test is to create a patch that sends 144, 60 and 100 in succession to the midiout object - this should start a middle C note sounding on an attached MIDI instrument.