µPad is an open digital note-taking app.
Try it today at https://web.getmicropad.com
There are a couple GitHub Project boards with what's in development. That board would also be a great place to look for cases to contribute to.
You will need the following:
git clone https://github.com/MicroPad/MicroPad-Core.git micropad-core
cd micropad-core/app
yarn
yarn start
yarn build