Primordial black holes are the candidate here as you mentioned (black holes exist, primordial black holes may exist, but we haven't found any yet). Thanks to L

Primordial black holes are the candidate here as you mentioned (black holes exist, primordial black holes may exist, but we haven't found any yet). Thanks to LIGO we think we may have the first evidence for them, but there is still a lot of work to do to prove them. Decent article on that: https://www.sciencenews.org/article/ligo-black-holes-dark-matter https://www.sciencenews.org/article/ligo-black-holes-dark-ma... The interesting thing will be if we can prove they are around, which would then give some options for showing if they're dark matter or not (looking for gravity waves in areas where there's large dark matter concentrations would be the most likely candidate for now).