"Most PBH theories assume these objects have masses like small planets, with event horizons as small as grapefruits. It's an outlandish idea, still on the fringe of black hole and dark matter physics, said Joey Neilsen, a physicist at Villanova University who was not involved in the new study. But recently, as other dark matter theories have turned up empty, some researchers have given the PBH notion a second look."
Over the years I read a number of reports on primordial black holes dating back to shortly after the BB event. It will be interesting to see if the PBH can be identified. There is also primordial neutrinos that should flood the universe today from the BBN period. These primordial neutrinos remain to be shown too.