Sorry I should have been more specific, I believe the edx cs50 has a discord group and a slack group with active students taking the course.
Ideally he should find someone also interested and take it together, from my experience learning hard things is significantly easier when you have someone to talk to whose also struggling.
There is a subreddit [0] for the class where the instructor (David Malan) posts frequently. Very helpful for asking questions and learning more!
[0]: https://www.reddit.com/r/cs50