The best alternatives to Rocketboard are A Web Whiteboard, Whiteborb, and Idea Paint. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Rocketboard?
Agree.com— Free e-signature for everyone with invoicing and payments!
Whiteborb is a shared online drawing surface. It's free to use and open source. It also doesn't require signup and works well on mobile devices. Give it a try! 🖌️
You can start drawing or note-taking just opening https://kakeru.app on your browser. Sending link of the page to friends or colleague, you can collaborate with them. You can write on PC browsers, smartphones, and tablets, including iPad with Apple Pencil.