I was just wondering where the support for ListenBrainz was… I found this thread asking for support to be added, but it is over two years ago and doesn’t look like anyone at Plex took notice.
I can tell you that your site works for me and your site’s step by step instructions make it very easy to setup. I will say that I’m okay with the webhook approach right now, but am not thrilled that I’m basically sending all my music listens through a third party to get to MusicBrainz. I’d much prefer if this was built directly into Plex Server. I don’t know, maybe it could be done as a plugin until Plex figures out that this is something wanted?
