The fact that many trans-Neptunian bodies have weird orbits is not a correct argument for the existence of an extra big planet beyond them in the present time.
It is only evidence that at some moment in the past there was something big out there, which has perturbed their orbits.
In 2024 there have been published a few papers which propose that a star has passed close to the Solar System in the past and its passage has caused all the unusual orbits that we see in the outer Solar System.
This seems more plausible than an undiscovered big planet.
It is only evidence that at some moment in the past there was something big out there, which has perturbed their orbits.
In 2024 there have been published a few papers which propose that a star has passed close to the Solar System in the past and its passage has caused all the unusual orbits that we see in the outer Solar System.
This seems more plausible than an undiscovered big planet.
https://www.nature.com/articles/s41550-024-02349-x
https://iopscience.iop.org/article/10.3847/2041-8213/ad63a6