What difficulty are you having and what have you tried to do to solve it? I have Sonos 1 kit I bought in 2013. I upgraded the OS on my iMac Pro to Big Sur and I continue to have access to my entire Music library via the Sonos app on my iPhone. I seem to recall I had to use the Sonos application on the iMac to re-establish the connection to the library after the upgrade, but I’ve had no difficulty since then.