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.
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!
Abiword and onlyoffice are good options too
Maybe Etherpad?
I like CryptPad a lot.
Collabora Office is nice too but I prefer CryptPad for my purposes