Similar to another post from July GitHub Learning Lab Course Page includes broken links I noticed that:
links to https://github.community/t5/GitHub-Learning-Lab/bd-p/learn (Oops! That page doesn’t exist or is private.)
So it seems to be a more general problem. Obviously I have found my way here to https://github.community/c/github-learning-lab/34 anyway, but it would be good to get the links checked and corrected where necessary.