Here are some good materials available on YouTube for free.
(Last update: 2022-04-20)
Computer Systems and Operating Systems
Computer Networks, Distributed Systems, and Cloud Computing
- Distributed Systems by Lindsey Kuper
- Distributed Systems at MIT
- Virtualization and Cloud Computing by Mythili Vutukuru
- Distributed Systems Reading Group
- Distribute My System
- Jim Kurose's Networking Videos
- The Networking Channel
Databases
Cybersecurity