If you’re on Ubuntu, you can just ask your question in the normal Linux community or in a search engine. You don’t need to go to a special Ubuntu community.
That’s at least, how it makes sense to me. In general, I’ve seen many niche distros have very active communities, because everyone just ruts together and helps each other out.
…which is to say, I don’t think there are accurate marketshare statistics, because no telemetry, but my impression is also that Ubuntu is still popular out in the wild.