Ask HN: Fast paced courses for experienced programmers?

Hi HN, I've always (12+ years) been a T shaped programmer, with a very strong (or at least relative) expertise in JavaScript / TypeScript, and some small knowledge on adjacent technologies like kubernetes for instance. By very strong I mean I know the syntax and the APIs like the back of my hand, the history of it, the major packages and their pros and cons etc.

Because of some changes at work, I'm looking into getting some additional knowledge on a few languages. First, on native mobile development with Swift and Kotlin, then on other backend languages, such as rust (because I want to) or PHP (because I have to).

But I'm struggling finding resources with the right pace. I'm initially looking at Android dev with Kotlin for instance, and a lot of it is either too shallow ("hello world" examples) or assume that you're a java dev with working knowledge of android dev just wanting to learn kotlin etc.

I've seen recently https://app.codecrafters.io/ for instance that seems close to what I want (although no mobile). Any other resources that you guys know aimed at experienced developers that don't spend a month covering basics, but also do go through the specifics of the language? Happy for any format (video, online exercises, books...) and potentially any price if the value is worth it.