Chosen Solution
Dropped iphone 8 on its bottom right corner (looking at the screen). Screen did not work afterwards, and upon plugging into a power source, phone was getting hot, but not responding to any of my clicks or touches. Eventually it stopped generating heat when i plugged it in.
Talked to Apple Genius, told me the battery is at fault but claimed all other components should be fine. So i undertook the task of replacing the battery as well as the LCD/digitizer myself.
Using the new battery and screen, when i plug into a power source, i get heating issue again, this time with the phone opened up i can feel the source, and it gets generated on the logic board, just south of the rear facing camera (near/on A11 chip). Screen still does not work, new battery does not get hot, Could the logic board be at fault here? Is there a potential short? Can i still somehoe recover my data?
First detach the camera flex and back camera connector from logic board and check.
It is quite common if a phone is getting hot, that there is a short circuit causing the heat. This is also quite common after a device is dropped. Larger Capacitors are generally the culprit and i would suggest if you have taken your phone apart, take it apart again and try to locate if a certain area of the board is getting burning hot vs other parts of the board that are not.
There are some great videos put together on youtube on how to detect a short on an iphone motherboard. Since you mention the heat, it is the first thing that pops to my mind.
Do disconnect the camera flex and back camera like @thegsmsoluion suggested though, as a fault in those components will stop an iphone 8 from booting. FYI it will be common for the A11 chip (the cpu) to get hot while trying to boot as it is making all of its calculations and gets hot.
