A small team of planetary scientists from the California Institute of Technology, Université Côte d'Azur and Southwest Research Institute reports possible new evidence of Planet 9. They have published their paper on the arXiv preprint server, and it has been accepted for publication in The Astrophysical Journal Letters.
This same group has been pushing this theory for a decade with no direct evidence. Each paper is just confirmation bias in action.
Some amateur types have been pushing this for decades with zero evidence, but as the article says, a legit pair from Caltech finally found some circumstancial evidence it could be possible, and this expanded group is just throwing more on the pile. I think it’s just one of those “Well…let’s say it’s possible, here’s what we’d be looking at for evidence…” kind of deals.