I personally preferred Andrej Karpathy's CS231n taught by him and his private videos about neural nets in general and transformers in particular. He has a youtu

I personally preferred Andrej Karpathy's CS231n taught by him and his private videos about neural nets in general and transformers in particular. He has a youtube vid where he builds one from scratch in Python! 3BlueOneBrown videos are a great complement to Karpathy's lectures to aid in visualising what is going on.