The statement paper link says this "To help find our Sun’s coldest and nearest neighbors, the astronomers of the Backyard Worlds project turned to a worldwide network of more than 100,000 citizen scientists [2]. These volunteers diligently inspect trillions of pixels of telescope images to identify the subtle movements of brown dwarfs and planets. Despite the abilities of machine learning and supercomputers, there’s no substitute for the human eye when it comes to scouring telescope images for moving objects."
This is astrometry via the ouch method, very painstaking
Here is the arxiv paper and abstract link,
https://arxiv.org/abs/2008.06396
Much astrometric study went into this. Here is an example, "...plus a candidate late T companion to the white dwarf LSR J0002+6357 at 5.5' projected separation (~8,700 AU if associated)."
The angular size and projected separation is based upon a distance ~ 26 to 27 pc from Earth.