Not sure I understand.<p>What prevents you from using a same identity to log in to multiple self-hosted instances?<p>I think it&#x27;s the same. As far as I get it - haven&#x27;t used Slack much - with Slack you either have to use different email address to create account for each team (subdomain), or you have to be explicitly invited. Or maybe I got a wrong idea. Either way, while I&#x27;m not sure all self-hosted alternatives have options to consume external identities (be it third-party leased ones like Google account or self-originating ones), at least some have those. Which means the authentication is fairly transparent.