They tend to be language or framework specific. e.g. for Ruby/Rails questions I haunt the GoRails slack and a couple of Ruby/Rails specific subreddits.

In quite a few cases the official dev forums for a particular vendor or technology are actually very active, and I think that's because forums just got a lot easier to implement. For example I get a lot back from the Apple Developer forums (not the public discussion community, which is hot garbage) and Vue.js's own forum.

A fair chunk of what I previously used Stack Overflow for (finding code snippets to learn from) has been replaced by the ease of browsing public repositories on Github.