FWIW, you may be interested in ListenBrainz[1], an open alternative to Last.FM. We're just about to launch the beta which should be the milestone for when we'll promise to keep submitted listens around Forever™. :)
Compare http://www.last.fm/api/show/track.scrobble 's 7 item specific metadata fields (artist, track, album, trackNumber, mbid, albumArtist, duration) to https://listenbrainz.readthedocs.io/en/latest/dev/json.html#... - as ListenBrainz is part of the MetaBrainz "umbrella", one of our own main highlights is that we can now actually submit all MBIDs associated with a file, not just the Recording MBID (ie., Artist MBID(s), Release MBID, Release Group MBID, Track MBID, Work MBID(s), possibly Label MBID(s), etc., etc.), but also stuff like language, performers, AcoustIDs, ...
Also, ListenBrainz is linked up with MessyBrainz[1], which should work as a buffer to have even listens submitted without MusicBrainz identifiers be able to eventually get linked up to the MusicBrainz database.