Slack Alternative Zulip 6.0 Releases With Massive Upgrades
Zulip is a free and open-source team communication platform that offers a range of customization options, unlike Slack.
We looked at it last year, and it seemed like a promising open-source alternative to Slack with its features and accessibility.
It is free to get started using its official hosted version on the web but comes with certain restrictions (like message history retention limit and no custom branding).