Me and my friend just want something to brainstorm and write our ideas down on. Cryptpad is a decent I’ve considered, it has rich text editing which I don’t need though it’s nice.
https://www.collaboraoffice.com/ is LibreOffice in the cloud.
Onlyoffice can also be self hosted as a cloud office solution (can’t remember if that one is 100% FOSS).
Onlyoffice
AGPL-3.0-only license, which from my limited knowledge means it’s FOSS. Collabora looks great! Though seems extreme for our use case.
Joplin has a sharing feature that allows multiple user editing of an entire notebook.
The downside is that both individuals need to have Joplin installed and either have Joplin cloud accounts or a self-hosted installation of Joplin server, which in either case may be more effort than is worth it for you.
Etherpad is a relatively lightweight option: https://etherpad.org
And you can find some server here : https://github.com/ether/etherpad-lite/wiki/Sites-That-Run-Etherpad
You want Gobby
We are using Hedgedoc a lot, and we love it!
if you’re looking for just a collaborative editor then there’s etherpad.
Abiword and onlyoffice are good options too