Zulip : Powerful slack-like open source group chat
Budibase : Budibase is an open-source low-code platform for creating internal apps in minutes. Supports PostgreSQL, MySQL, MSSQL, MongoDB, Rest API, Docker, K8s
GitLab : GitLab is a web-based Git repository manager with wiki and issue tracking features. GitLab offers hosted accounts similar to GitHub, but also allows i...
cal.com : Open source meeting scheduling tool. Send a link, let others book a slot. Calendly alternative.
Riot : Riot allows teams to communicate across a wide range of collaboration apps. If some team members use Riot while others use IRC, Slack or Gitter, Riot ...
Lemmy is a selfhosted social link aggregation and discussion platform. It is completely free and open, and not controlled by any company. This means that there is no advertising, tracking, or secret algorithms.