The device port can only send to a USB MIDI host (i.e. a computer). There are MIDI Host adapters out there that might work, but I haven't tried them.
Alternately, the MIDI In port can be used as an output and an input, using a cable like this to split it:
https://btpa.com/GMIDIY1-II.html?category_id=138
Is it possible to just connect a midi cable to that port and use it as an output?