I actually started a newsletter [0] on growing as a T-shaped developer after I didn't find anything similar online that scratched my itch. I try to do one or two small explorations a week in different areas of tech that I wouldn't normally come across in my day job as a front-end engineer, and I decided to send them out to others too!
I like the metaphor of a T-shaped developer, which is why I mention it on the site. I decided on "Breadth First Growth" as a cute way to convey the focus on growing sideways (and reference the search of course). It's mostly geared towards junior developers and those without a solid CS foundation, so although I might not recommend it for the average HN reader, I've heard good things about it from other junior devs and bootcamp grads. It's been great to make and share!
[0] https://breadthfirstgrowth.com