There are a couple of protocols that do similar things, but nearly all of them have a major fatal flaw, that is unfortunately very difficult to work around through no fault of their own: mobile push notifications, especially on iOS. An open protocol is useful, but not enough, and that&#x27;s where Slack hosting and developing everything themselves has an advantage, despite open protocols and tools being what I&#x27;d normally want to use. But practicality matters, and so when I last looked at alternatives a year ago, I couldn&#x27;t find anything that would be a drop-in feature-complete replacement. It&#x27;s a shame, but I expect something to come up in the future, perhaps on Matrix or other protocols.