It's no reddit in terms of quantity but honesty I've had higher quality topics and discussions here than there. Lemmy/kbin might not have taken off in the mainstream to offer a variety of subjects but when it comes to tech and software I think it's covered well enough and people are generally nicer about it. The main problem is lack of (remotely) good seach function, I dont think the threads are getting indexed by google and the on-site search is atrocious.

I don't know of any discord programming communities, I wish forums were still a thing but the only live one I know of is the jellyfin one after they moved from reddit. Other than that it's here or the various subreddits