The question of canon is something that can be more confusing in anime than it strictly should be. Many different series have different alternate universes, movies that are questionably canon, and supplemental materials that may or may not factor into the canon of the main franchises. Anime has a loose grasp on canon at the best of times, and shōnen anime may be the worst offender. While there has been a recent trend toward making movie supplements canon, such as Mugen Train and (tentatively) the My Hero Academia movies, there are still plenty of anime that will throw things in that are never referenced again or quickly forgotten and become questionably canon.
Source：https://www.cbr.com/is-dragon-ball-gt-currently-canon/
