Nextcloud Office is the document collaboration service of the Nextcloud suite. Nextcloud is a open source file hosting service for self-hosting. Nextcloud Office is part of the Nextcloud suite and is based on the open source tool Collabora Online.
Nuclino is a collaborative document editing service from Germany.
CryptPad is an open source document collaboration service that can be self-hosted. CryptPad is zero-knowledge, which means that the operator cannot read the content written on the site. Since it can be self-hosted there are many instances. The most known, which is also driven by the main developers however is cryptpad.fr.
