Not likely possible. The late Stephen Hawking established that black holes evaporate as well as accrete. The smaller they are, the more evaporation dominates accretion. So any sub-stellar-mass singularities from the early universe have long since gone.

A pity in some ways. It messes badly with a number of good Larry Niven stories from the days before Hawking made that discovery, for example. But then the Vikings and Mariners did a lot of damage to a lot of Heinlein’s stories too. They all still make good stories.

I am hoping “Planet 9” is a primordial black hole mystery, if it exists at all.

We could do a lot with that

I still prefer PBHs for dark matter, but axions are fashionable as they also solve the strong CP symmetry problem

https://en.wikipedia.org/wiki/Axion

it’s hard to say what else could be responsible but as they say, high-energy gammas are tricky as evidence

still, quite interesting

should help lead to confirmation within a few years, we’re getting close