I love how Sonos response to the limited library is use someone else’s software and pay for their subscription. Music fans with large libraries can go pound sand.
Plex isn’t good for playlist imports. But….
Roon is expensive as heck. However Roon streams perfectly with the Sonos hardware and even does whole home playback. You’re no longer stuck with the Sonos app and even no longer stuck in Sonos hardware ecosystem.
Try the Roon free trial