CryptPad is a collaboration suite that is end-to-end encrypted and open source. It includes text documents, spreadsheets, presentations, forms, kanban boards, diagrams and a code/Markdown editor, plus a drive for organising files. Changes sync in real time and all user data is encrypted. You can use CryptPad through its flagship instance at cryptpad.fr, through other public instances, or by hosting it yourself, for example with the official Docker images.
CryptPad is developed by a team at XWiki SAS, an independent European open-source company with staff in France and Romania. The software is licensed under the AGPL-3.0. The flagship instance is funded by subscribers and donations; earlier funding came from a French state research grant and European programmes, among others. When self-hosting, the data stays under your own control, but users still rely on the administrator to serve trustworthy code, because the encryption code is loaded from the server.