Matthew Weidner was a student of Martin Kleppmann. He made collabs, a typescript CRDT library similar to Yjs or Automerge.
As a transport protocol he uses a matrix group chat, which I find really interesting. The app itself then is displayed as an element custom widget.
In the single user case, you could just make it in the weekend, put it up and forget about it.
Basically at this point, you are thinking of quitting your job and starting a startup, all just to add collaboration to this app.