Chosen Solution

My cameras and flashlight are no longer working. What physical part would I replace internally to fix this?

I agree. Let’s try a force restart first How to Force Restart an iPhone 6s Are any of your cameras working? Often times when one camera doesn’t work, you don’t have access to either. Could be worth your time to take a peek inside, see if your water damage stickers are lit up iPhone 6s LCD and Digitizer Replacement