As it turns out, not much about investigation. I looked through the curriculum at Berkeley[1] (a respected journalism school) and found things like J260[2] which is a seminar more on "why" of investigative reporting than the "how". There is also a "web skills"[3] class, but this is just about building a web site.
They really should consider adding a 'using the Internet to find people, corroborate sources, discover links between individuals and corporations, and to track ownership relationships.' Something that, as the author points out, is really a bunch of useful web sites and how to click them.
[1] https://journalism.berkeley.edu/curriculum/
[2] https://investigativereportingprogram.com/
[3] https://journalism.berkeley.edu/course-section/j215intro-to-...