The collaborative experience is heavily desired  one as it is most intuitive to actual brainstorming. Here are some examples: 

- [Jamboard](https://workspace.google.com/products/jamboard/)
	- around for years but to be discontinued
- Apple's FreeForm 
- [Ziteboard](https://app.ziteboard.com/)
- Canvas feature on here 
- [Miro](https://miro.com/apps/) 
- [Mural](https://www.mural.co/) 
- https://www.fabrie.com/home
- [Excalidraw](https://excalidraw.com/) - the fantastic app used in Obsidian