There's Hoopa rings randomly appearing everywhere. Do they do anything?
They’re just for visuals
Hoopa’s rings are there because of the game’s current events-they first came when all the legendaries appeared in raids during the GO fest to make it make more sense lore-wise. They’re here now to make the introduction of gen 8 Pokémon make sense. However, they cannot be interacted with-they’re just there for decoration.
Source: This and experience.