Chosen Solution
So, a friend gave me their iPhone 6 that had a third party screen repair. The screen worked on another device at the third party repair location. The repair shop tried a different screen and it did not work on the phone. The repair shop guy said that sometimes the motherboards go bad in the phones, but the phone still powers on and makes noises. Is the phone screwed? My friend would like their stuff off the phone but I cannot get the screen to work to retrieve their info.
Have a look at the phone with a torch or the likes pointed to the screen, it might be is “just” a backlight problem. If that’s the case with the help of such light source you might be able to see/guess accurately enough to get into the phone to start an itunes backup and save your data. Otherwise you’d need an experienced technician specialized in microsoldering who would be able to fix the phone/recover data for you.