/r/embedded tends to be pretty decent. Of course it's highly specific to embedded development, but the better subs tend to be the more narrowly-focused ones.

r/programming is pretty solid, from what I recall, although I don't go on there often. I used to frequent r/scala when I was actively using that language, as an example of a niche. My reddit front page, with my idiosyncratic collection of subs, often produces a comparable amount of joy to the HN front page, but in a different set of verticals than here.