Physically, you should be in the clear to make the swap. The two issuses are that the iPhone SE 2020 display has different features/firmware then the iPhone 8, and the battery is different. As long as your only using the housing of the iPhone 8, and just transfering all the components of the iPhone SE to the new housing, you should be fine. In additon I would also [product|IF435-001|purchase a new SE battery] rather then try to use the iPhone 8 battery.