Are there any good, in-depth courses that don't require watching videos?
For others, https://web.stanford.edu/~jurafsky/slp3/ will take you a decent way to understanding transformer architecture.
I've been making a course that has a little less theory, and a little more application here - https://github.com/VikParuchuri/zero_to_gpt . Videos are all optional (cover the same content as the text).