That is what I am trying to figure out. I developed this on a Pi using the python virtual env setup. This would put the files at /srv/homeassistant/lib/python3.8/site-packages/pynuvo. I followed Brian’s instructions in post 11(Legrand Nuvo multi-room audio support). I am not sure how the hassos handles this now.
EDIT: Looks like we are running into the same issue as these guys: Components require additional python code/library . Since hassio is in a container, you can’t access the libraries to modify them. There is discussion there about loading a library with the integration (so my version of pynuvo would live in the custom_component directory). I don’t have a good way to test that right now, but you guys can hack away at it.