Isn't Reddit a "forum as a service"?
Yeah, I'm not sure how this isn't being mentioned more. It's simple to setup a subreddit, posts can be filtered with tags, and can be private or public.
Seems exactly what the original poster would be looking for.
I agree that Reddit is probably the platform that resembles more like a Forum
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.