I don’t know if this has been in conspiracy yet but I wanted to address it: 

Dialga, Palkia and Girintina are actually Ultra Beasts.

Now hear my out. In the after story of Pokémon Sun and Moon, the Looker states that something happened about 10 years ago. Pokémon Diamond and Pearl came out about 10 years ago from the release of Pokémon sun and moon. The looker then speaks of a case of chasing down an Ultra Beast and how no one knew them as UB’S at the time.

10 years ago the Looker was in the Sinnoh region and the incidents with team galactic & dialga/palkia occurred. Dialga and Palkia (not to mention girintina) both came out of portals from other dimensions much like Ultra Beasts. Not to mention they look like Ultra Beasts and fit all the standards to be Ultra Beasts.

So yeah, dialga, palkia and girintina are ultra beasts. Have a good day.