Amongst all the made-for-YouTube content that others have mentioned, it's also worth remembering that many universities will publish entire courses for free. Christof Paar's Introduction to Cryptography lecture series [0] comes to mind for example, as does MIT's Missing Semester [1].

Also, if you're interested in Rust at all, Jon Gjengset is great: https://www.youtube.com/c/JonGjengset

0: https://www.youtube.com/channel/UC1usFRN4LCMcfIV7UjHNuQg

1: https://www.youtube.com/c/MissingSemester