TipTap
TipTap is a ProseMirror based editor that integrates Yjs as the collaborative editing solution. It has a rich ecosystem of extensions and integrates well into web frameworks (React, Vue, ..).
Headless WYSIWYG Text Editor – Tiptap Editor
They have a great getting-started guide for collaborative editing with Yjs & TipTap:
Collaborative editing – Tiptap Editor