Wow! That’s an impressive list. Thanks for compiling it.
I created a dev-news tag and added all those topics to it, to see how it feels. If it’s good enough, we can stick with that and not create more hierarchy in the categories.
I noticed the #announcements category description says “The place for all Discourse announcements.” Is that accurate? Are there more 
PSA type announcements that are shared in other categories? I know we have #releases as well which is also contains announcements of a sort.