Why people switch: Message history limits and data residency rules push teams to self-host.
-
Mattermost
The enterprise-grade drop-in; strong compliance story.
MIT/AGPLself-hostable -
Zulip
Topic-threaded model that actually scales to async teams.
Apache-2.0self-hostable -
Rocket.Chat
Chat plus omnichannel customer messaging.
MITself-hostable