USEnet has been dead for some-for two decades and was alive long before compuserv came along and moduled into it. The fact you mention it as the 'dark web' is suspicious as if you are familiar with other darker uses of the Internet.
The fact that you suspect a major vehicle manufacturer inspecting a platform like this is pretty hilarious. Enthusiast clubs are found on the aforementioned forums and shit like Facebook groups, which I'd imagine 90% of their buyers have the patience and the tech know-how enough to be apart of a group on Facebook on their cell phone and that's about it.