For a collaborative text editor, you need two things: (1) a full-stack system that maintains a running list of data events such that everyone sees everyone else's events eventually, and (2) frontend code that adapts that set of events, along with your text cursor position and current changes, into a cohesive view of a document at any moment in time.

Supabase and Replicache can absolutely help with (1). But for (2) you will need OT or CRDT.

https://docs.yjs.dev/getting-started/a-collaborative-editor is a good place to start - it uses Quill and CRDTs for (2) and can have a persistence layer built in (or custom written, to work on top of Supabase etc.) for (1).