You can go after Udemy. They're not just a hosting service. They claim ownership of the content. "Each of our 35,000+ courses is taught by an expert instructor". Many courses are paid. If Udemy charges for access to the course, they lose the DMCA safe harbor. Then they're liable for full copyright damages.
This may even be criminal copyright infringment under 18 U.S. Code § 2319 (Criminal infringement of a copyright) if the total retail value exceeds $2500.
This may even be criminal copyright infringment under 18 U.S. Code § 2319 (Criminal infringement of a copyright) if the total retail value exceeds $2500.
Get a lawyer. This looks winnable.