Reference:

• How do I get started in theoretical CS ?
• Introduction to Theoretical Computer Science - Boaz Barak
• CMU 15-251 Great Ideas in Theoretical Computer Science
• MIT 18.404J Theory of Computation, Fall 2020 - Home Page
• Undergrad Complexity at CMU - Home Page
• Graduate Complexity at CMU - videos
• CS Theory Toolkit at CMU
• What Books Should Everyone Read?
• What are the recent TCS books whose drafts are available online?
• What papers should everyone read?
• What videos should everybody watch?

There are some additional subjects mentioned by Sipser's last course:

• MIT 6.841/18.405 Advanced Complexity Theory
• MIT 6.875 Foundations of Cryptography - Spring 2018 videos - Fall 2021 videos
• MIT 6.842 Randomness and Computation

Except for MIT 6.875, other additional courses don't seem to have public videos, if you find them, I'd appreciate it if you could let me know.