By having player 1 interact with a fortune teller at the same time as player 2 exit the hut, the UI will remain hidden.
This does not hide the beat bar, which can be hidden separately in options.
This also does not hide the dungeon minimap.
This persists through save files and you exit out of it by talking to a fortune teller again.
You can hide UI by interacting with this NPC as player 1, and having player 2 exit at the same time. Good for screenshots, etc. pic.twitter.com/zfuwoEv1p3
— CloudMax (@CloudMax94) July 23, 2019