There’s some discussion in this forum on the “indieweb”, and implementing “webmentions”, which you might want to search for. I think that’s similar functionality to “backlinks” in a way. But, hugo itself isn’t a wiki, so this sort of thing depends on outside programs iirc.
Haven’t tried this locally, and it feels like it might be a performance killer, but I could see you creating a shortcode for links inside your content, then creating a partial for part of your templates that loops through all pages, checks for .HasShortcode, and then compares, for example, the passed value (in your shortcode) with the base filename of the page.
The documentation site has a very powerful search :
Looks like a cool wiki tool. Hugo is a super flexible and powerful static generator that can create all different kinds is sites and beyond, including multiple output formats. RTD. HTH.