There are more than one billion public playlists available on Spotify. But as far as I can tell, the only way to search for them is to enter a word in the universal search field (I mostly use the desktop client for Mac), scroll down in the instant results and click the "Playlists" category.
At that point you can scroll through a variety of resulting public playlists that include the search term in the title of the playlist. But you cannot search for song or artist or album in a playlist. And there appears to be no order to the search results (maybe it's alphabetical, but this isn't useful). Some playlists are just a single album. Others are an artist's entire body of work. You wouldn't know what is what without clicking into each and every playlist.
Is there any way to sort playlists by followers, filter by date last updated, or otherwise search all public playlists to return more relevant results?
(There are a few relevant questions at Stack Overflow re: this request, but I haven't yet found a service that actually implements any of these searching/sorting functionalities.)