For sharing local music (in this case it's all in iTunes/Apple ecosystem), normally we would use Apple Music, or before that came out, Google Music with Media Manager software.

For client (assistant) imposed reasons, they are looking to avoid that if possible, and want to keep the sharing of the local music library across a few geographically separate properties "in-house".

From my searches it appears that there's no good way to do this, because the Sonos Music Library uses SMB. Just wanted to double check here: Local folder shares over the internet isn't a viable option right?

Thanks.