Not really a course, but Harry Potter and the Methods of Rationality is a pretty good fanfic made with the intent of teaching critical logic concepts and logical fallacies to the reader. I found it a good read, and even if you might dislike some of the literary choices made (Harry makes fast friends with Malfoy, etc), it does cover most of the stuff in a critical thinking textbook in a somewhat approachable manner. It’s free, and you can read chapter by chapter if you just want to give it a glance.