I have a massive digital music library that used to reside in iTunes (on my Mac and on an external hard drive). When I upgraded my Mac OS to Big Sur, iTunes was eliminated and I lost all Sonos connectivity.  

All!  

Apple, Sonos and lots of crying didn’t help.  

So, as a relatively computer illiterate but passionate music lover with 2 TB of music, I buckled down for 3 weeks, taught myself and experimented.  

Here is what worked for me.

1. Go through all of your songs and eliminate duplicates.
2. Get a new external hard drive (one with an extra TB than you need), erase it, and convert filing system to Mac OS Extended (“case sensitive, journaled” worked for me).
3. Move all of your previous songs to the new, clean, re-formatted external hard drive.
4. Go to Sonos to manage your sources and add new external hard drive to connect...also, eliminate any previously utilized pathways that are no longer active.
5. You can still access some music on your computer, but have to also add that as a source  in your Sonos preferences.

Good luck.

This is so scary, but I have had connectivity for 6 days and still going...