What is the best online course for learning cyber security?

Answer 1

You can find many courses from freecodecamp, edureka, coursera, udemy etc. But most of them are paid. Check out this playlist:

https://www.youtube.com/playlist?list=PLtaCDNKzacY5Tx5pSZGYssD2mAVSWobPn

It can help you to learn cybersecurity, penetration testing, linux, c etc.

Answer 2

Offensive Security, if you google and tor-gle, you'll end up on some free stuff, offered by them.