Some of these may require you to register but should be absolutely free without a “trail free period” with the of a credit card.

https://www.coursera.org/learn/fundamentals-of-machine-learning-and-artificial-intelligence
https://www.coursera.org/learn/ai-security
https://www.coursera.org/learn/responsible-artificial-intelligence-practices

https://ocw.mit.edu/courses/6-034-artificial-intelligence-fall-2010/resources/lecture-videos/