@paul Frame challenge: you say you are learning web development, but React is, like, the antithesis of web development. (It has some good ideas, so it can be worth learning about the framework, but actually using it is another matter entirely.) I doubt you'll learn best practices from this codebase.
As for an entry point… I don't know about "good", but __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED is a funny entry-point.