During FOSDEM 2025, a conference about freely distributed software, Thorsten Behrens, a LibreOffice hacker, presented:
Distributed real-time collaboration for LibreOffice Writer - a first prototype.
What's that?
This is a mode where multiple people, each with their own local copy of LibreOffice Writer running on their own machine, can all work together simultaneously on the same collaborative document.
In essence, it's like Google Doc, but you don't need a third-party server; you don't need to work in the browser; you don't need to be online:
It's the same sort of functionality that you get from Google Docs. [...] The big difference is that such tools [Google Doc] run in a browser, so you need to be online. What makes the CRDT implementation different is that this is a local app, working on a local file, but using a network copy to keep changes in sync. The idea is to free you from keeping your apps and data on someone else's computer, without losing the handy collaborative features that web apps bring.
Source: https://www.theregister.com/2025/02/13/libreofficewasmzetaoffice/