Usenet is the network of servers using the NNTP protocol to exchange messages (called articles) across the internet. It used to be pervasive, with most ISP’s creating their own server for their customers. Today, it’s very much a niche, and you have to find a server to use it, and any server worth considering is going to cost money for a subscription. You also need to pay attention to whether or not the server supports all the binary groups, as that’s the ones you would be interested in. Servers supporting binary groups will have two ways to pay - a recurring fee for a time period of access (i.e. per month), or a one-time fee for a set transfer amount, which you’d renew if/when you run out.
You can find and download an NNTP client, or use the web interface of the Usenet provider if they have one.
Once you’re connected, you search for the news groups you’re interested in, which I’m guessing will start with “alt.binaries.erotica”. All messages are in 7-bit text, so files are encoded (UU, Base64, Yenc, or maybe something even newer by now).
There are, of course, tens of thousands of categories about just discussions. Think of it as collection of forums, but without any baggage. It’s just a series of messages (“articles”) written by people to a specific group, with other people responding. Usenet was around long before the web, much less web-based forums.
For clients, you may as well start here to begin searching.
For servers, just do a search of NTTP servers. Look up their retention times, in particular for binary groups, as that’s what will determine how far back you can search for things.
The only one I’ve used anytime recently is Astranews. I paid them $25 for something like 100GB back in 2006. I still have over 70GB left, and my account remains active, even though I haven’t used it in quite a while. The client I used in the past on Windows was Forte Agent.
I just had a quick look and didn’t see any groups obviously catering to VR, so it may be you’d just have to look in the particular genre you want for VR videos, assuming anyone’s actually uploading them.