When I join or create ANY world in 20w22a, my camera is flipped upside down. The game functions as normal, just upside down. Gravity is the same, physics are the same, the player model is fine, it's just an upside-down camera. To be clear, if I join the world in a previous snapshot, it is totally fine. It only affects this snapshot.

EDIT: I've found out it is also mirrored if that helps.