This hour-long MIT lecture is very good, it builds from the ground up until transformers. MIT 6.S191: Recurrent Neural Networks, Transformers, and Attention: https://youtube.com/watch?v=ySEx_Bqxvvo
The uploads of the 2023 MIT 6.S191 course from Alexander Amini (et alii) is ongoing, periodical since mid March. (They published the lesson about Reinforcement Learning yesterday.)