I have a free Spotify account and via the sonos plugin I have added Spotify playlists to my playlists in sonos.
They show up in th list with Favourites.
I have not looked in the program code but we had this issue with a different app.
The spotify playlists are returned by the sonos api when you retrieve all the radio stations favourites.
In the json which is returned for the favourites you find the Spotify playlists with a type field which has the value playlist.
I hope this helps you to get the spotify playlists filtered and joined into the real list with playlists like we do.
I have a free Spotify account and via the sonos plugin I have added Spotify playlists to my playlists in sonos.
They show up in th list with Favourites.
I have not looked in the program code but we had this issue with a different app.
The spotify playlists are returned by the sonos api when you retrieve all the radio stations favourites.
In the json which is returned for the favourites you find the Spotify playlists with a type field which has the value playlist.
I hope this helps you to get the spotify playlists filtered and joined into the real list with playlists like we do.