In scripulous mansion, if u go to the top door, then after u enter the door, go to the right and try to fly up to the ceiling bc there is a hidden roof that leads you to another door above, after u enter that door, go to the right until u see a black void looking place with two blocks one on each side, then u will need to fly and hug the wall bc there will be a invisible platform there. Keep going upwards and you'll reach the challenge.
(PS: U need propeller mushroom for this)