Thank you for the nice comment :-)
Currently it is not possible in Sound Show to have the sound replicated on multiple output devices. That's definitively something that I would like to add in the future.
In the in the meantime, you could use external software to achieve the routing of the sound. If you are on Windows, you could use the software from https://vb-audio.com/
Thank you so much! I'm giving it a shot as we speak. Though, for some reason, SoundShow fails to send audio to the VB Cable as soon as VoiceMeeter is installed... Hoping I can figure a workaround for this quickly enough.
EDIT: Just in case anyone runs into this same issue, my fix was to route SoundShow into OBS, OBS into the VB Cable, the VB Cable into VoiceMeeter, and then that worked.