Thought this was worth a message, as I've been struggling with Sonos/Spotify for the last year, to the point I stopped using it due to frustration.

Like lots of others on here, Sonos worked OK via Spotify app. Using Spotify through the Sonos app resulted in dropped connections all the time.

Lots of reading, contacted Sonos support etc but never got anywhere with all the updates, resets/reboots/re-authorising accounts and clearing playlists etc. All appeared temp fixes.

Pleased to say all is now working fine by adding a traffic rule to enable the mdns setting:

Address 224.0.0.251

Port 5353

Screen shot below showing more, defo worth checking your router settings or googling this to set up your router if you've got the same issues!

For info, if relevant my split s1/s2 system is connected wirelessly to a 5g teltonika TRB500 gateway via Devolo magic 2 homeplugs so totally off the supported setups list!!