I do not use whisparr specifically, but generally for the *arrs you can use jackett to support way more sites. It essentially converts site specific data formats to well known formats that the *arrs support.
Or use prowlarr and sync downloaders/indexers to all *arr apps with 1 click.
Never used whisparr either, but it looks like there is enough feature parity with the other *arr apps that it'll probably Just Work™ out of the box with prowlarr.
I don't know, add the sites where the content that you want can be found. I think Jackett also had links to the regular web pages if you want to look around.
Ah, I see, then my apologies for making assumptions. If you're a Usenet person then things like drunken slug or Ninja central assist to have a bunch of adult content on them.
For torrents, you'll hopefully be able to find content on various generalist torrent trackers or a few specialist ones that primarily deal with that kind of content.