Kinto : Kinto is a lightweight JSON storage service with synchronisation and sharing abilities.
Garage : An open-source distributed storage service you can self-host to fullfill many needs.
CryptPad : CryptPad is the Zero Knowledge realtime collaborative editor.
Encryption carried out in your web browser protects the data from the server, the cloud ...
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 ...
Mattermost : Mattermost is a self-hosted solution for bringing all your team communication to one place, and making it searchable and accessible anywhere
droppy is a self-hosted file storage server with a web interface and capabilites to edit files and view media directly in the browser. It is particularly well-suited to be run on low-end hardware like the Raspberry Pi.