Twist Alternatives for Mac OS X

Mattermost is an open-source, self-hosted platform for secure team collaboration, offering a Slack-alternative with emphasis on data control, privacy, and customizability. It provides a range of communication and project management tools for distributed and technical teams.

Zulip is a powerful open-source group chat application designed for team collaboration. It uniquely structures conversations around topics, enabling users to easily catch up on important discussions and manage information overload. Zulip facilitates secure communication with integrated file sharing and various integrations.