Has this changed?!!?! OMG. Happy day!
I think I remember you once saying that only one Plex account could be linked to a Sonos account.
(Found it: Plex home user streaming to sonos (2020) - #2 by MovieFan.Plex. I was able to link the account, so maybe that part has changed!? But I don’t think that’s sufficient to enable Sonos control from within Plex apps. I think it’s gated behind a Plex Pass.)
Edit:
Can you confirm this information, @MovieFan.Plex?
I linked an additional Plex Home User account to my Sonos account.
Unless it takes a while to activate, I believe a Plex Pass is still required.
I signed out and back in to Plexamp, Plex.app, and Plex Web.
Sonos targets still don’t appear in Plexamp.
Plex.app and Plex Web still display “Upgrade to a Plex Pass …”.