ASK HN: Which subject (in CS/Dev), you want learn 'n didn't find good resource?

I'm a software developer for more than 15 years now, and I have a youtube channel with few videos about programming (right now specific about Rust but eventually much more). But as there so many sites, youtube channels, etc that teaches all kinds of stuff, I was wondering if what is the most "needed" area of knowledge to somebody try to teach in a better way, or even try to be the first to really teach.

So, if you want to learn something related to programming just comment on this post and let us know, maybe others from the community could also bring some new content about that topic for you.

It could learn specifics about one programming language, or some CS concept that you still didn't get, or even new technology like some specific deep learning or blockchain topic, etc.

Well, anything.