Dag Jop,
Welkom op het AntennaPod-forum 
This was also requested on our the developer platform GitHub, because allegedly Sonos looks in the ‘Podcasts’ folder of a device. The option to choose the precise location (so that you can set pick the ‘Podcasts’ folder) is also requested on GitHub.
However, I now understand there’s a Sonos API, @tonytamsf? Can you share a link to the specification? If there’s a specific API that we can implement, I guess we should reopen the aforementioned #2920?