Yumi's and Painter's planet seem to be in the same system (Yumi's planet is heavily implied to be the one seen from Painter's world which they first assumed to be a star, and there is Hoid stating that the two languages are related -->"Yumi and Painter’s languages shared a common root") so we can likely scrap that theory, unless Tress or Yumi/Painter somehow end up in another solar system, which is pretty unlikely considering the narratives.