I have a notification showing over 100 times a day. It says this phone/media output I've blocked every notification in my music, I've cleared data and cache in media and Spotify. But it still shows, it also stops Spotify from playing. It's driving me crazy.
Maybe worth uninstalling the app the notification is coming from, then reinstall it again and block notifications from the beginning. Clear cache and data for the app first, before uninstalling.