Dolibarr is an open-source ERP CRM software suite. It includes all the important features of an ERP CRM suite. It is used by millions of users worldwide.
Nextcloud is an open-source industry-leading on-premises collaboration platform. It’s a safe home for all your data.
Flarum is the next-generation forum software that makes online discussion fun. It’s simple, fast, and free.
Wekan is an open-source kanban board that allows a card-based (moved around) task and to-do management.
Rocketchat is an open-source popular Team Collaboration Software that should replace email, HipChat, Slack & Microsoft Teams. Rocket Chat has a lot of features.