The various public Etherpad instances are good. There are some that don’t require login (good for sharing public notes, bad for private documents), and some that do (better for private documents, gives you user access controls i.e. who can modify or read the notes)

Framapad is one that needs a login, but there are plenty of other Etherpad instances.

Alternatively, I heard lots of people like Nextcloud Notes (you can use a public instance or use a VPS)