Question: what do you do after you beat team rainbow rocket?
Answer: Team Rainbow Rocket Quest. Team Rainbow Rocket is an entirely new quest line that is unique to Pokemon Ultra Sun and Ultra Moon. ... 
Catch Lunala or Solgaleo (as well as the Island Guardians) ... 
Collect Totem Stickers. ... 
Fight at the Battle Tree. ... 
Bonus: Catch Em All.