This next suggestion is not like something from the darkest, forgotten corners of YouTube kinda obscure but for a film that had a mainstream release I don't think it's very well known. It did receive a lot of critical acclaim:

The Wolf House

It's a foreign language adult's stop-motion animation film that draws directly from the story of Colonia Dignidad in Chile.

If you haven't heard about Colonia Dignidad and you're interested, I can bring you up to speed on the backstory (there's benefits to watching it both with that foreknowledge and without it though.)