FYI, very recently (as in this has been in the news the past few days, and the article is from December) an article was published that suggested we might already have experimental evidence for dark matter being primordial black holes, though there are reasons to doubt it as well. I just posted the article: https://news.ycombinator.com/item?id=46955545

But this might be easier to read: https://www.space.com/astronomy/black-holes/did-astronomers-...