On the Cardano Roadmap home page, there is a link for Stack Exchange. Unfortunately, this page has been deleted for inactive activities. Maybe the Cardano Roadmap webmaster should remove this link for now since it has been deleted. Or maybe, we as community members, should start adding content. My humble suggestion.
Good catch @FiconTozo. I think it came a bit early due to the lack of community developer engagement at the time it was launched which was unfortunate.