The official React tutorial is one of the best ways to start using React because many other tutorials quickly fall out of date while this one tends to stick to the basics that are relevant to beginners.
This Modern Django 4-part tutorial series is well-done, has freely available source code and includes:
Django REST with React (Django 2.0 and a sprinkle of testing) combines a Django plus Django REST Framework (DRF) backend with React on the front end and shows how to stich it all together.
Build a Simple CRUD App with Python, Flask, and React shows how to combine a Flask backend with React.
Learn React app is a Git repository with a code tutorial and instructions for how to follow along, as well as exercises to ensure you are tested as you go.
9 things every React.js beginner should know is not a tutorial but instead the author gives some strong opinions for what beginners should know as they start learning React.
React interview questions is a good quiz to see what you know or still need to learn about the fundamentals of using React.
Under-the-hood-ReactJS examines the React codebase itself rather than teaching you how to use it.