This plugin is now bundled with Discourse core as part of Bundling more popular plugins with Discourse core. If you are self-hosting and use the plugin, you need to remove it from your app.yml before your next upgrade.
Not sure where else to report this:
The chat integration should be more careful not to show truncated urls in the body excerpt. For example, the matrix notification from this discourse post included only part of the ycombinator url, creating a link to https://news.ycombinator.co which is a rather spammy/scammy-looking site.