Well one the latest PBH hypothesis just released (called: "Primordial black holes from a cosmic phase transition: The collapse of Fermi-balls") has it all down to just PBH's!

I made a comment above in more detail about it, with a link to a discussion.

Whether or not it will turn out to be correct, or a better candidate will be eventually found... for now... who the heck knows?!

I just hope they solve this mystery in my lifetime, because the suspense of this puzzle has me so curious. Plus many are now wondering: do we need to extend current known physics, or invent entirely new physics to finally explain this?!

If so, how can we get any hints of a baseline to start with, to being fathoming this new physics? Do we need to invent ultra-hyper high energy particle accelerators to accomplish it?

I hope not! I hope the answer is easier than we suspect.