Spotify Web Connect Release Notes – Rithum Help Centre

Requirements

Sonos players aren’t available as devices (but the Sonos integration can be used for those)
Not all devices behave the same, e.g. smart phones become unavailable when locked or devices might become unavailable after a period of inactivity. Before reporting a fault please check/test with the player at https://open.spotify.com/ as this appears to be using the same API. Note that the available devices might not always be the same as those shown in the Spotify applications
The Spotify Library list is a combined list of playlists, albums and shows from your library and is limited to 50 items of each of those
Due do devices not being permanently available and appearing/disappearing frequently, the zones filtering feature is not available. For this reason the Screens > Media Screen > Enable zone filter setting should be turned off