I use Mattermost and don&#x27;t miss slack except for mobile apps. They released an OSS iPhone app for it recently and the Android one is about to be released.<p>Self-hosting, unlimited history, unlimited team size. They have great deployment docs for various methods and it was pretty easy for me to containerize it for docker.<p>It has a slack compatible webhook integration so many slack integrations will &quot;just work&quot; with mattermost, if the integration will allow you to specify your own url.