Samsung Galaxy Tab 4 (SM-T535) - The tablet does not start, how to diagnose?

Hello, (I don't know much about electronics, that's why I need support)
I got a Samsung Galaxy Tab 4 (SM-T535) brick to look inside and see if it can still be put on its feet.
I do not fully know the circumstances in which it stopped functioning. The only relation I reached was left on the charger (as every night) and in the morning he did not get up.
I do not know much about it so asking for help in diagnostics whether the problem is a battery, screen or something on the motherboard.
Attempts to start HardResetu also do nothing because there is no reaction.
symptoms:
Nothing happens when you try to start (no screen response, no vibration or backlight of buttons below the screen)
I tried charging on various chargers (including factory ones) without effect.
Meter indications:
Battery voltage disconnected battery from the board - 3.86V
Voltage on board disconnected battery from board + power supply (5V 2.3A charger) - values from 4.06V to 4.35V (jumps)
Battery connected to the board without power supply (measured at the connection of the battery with the board) - 3.86V
Battery connected to the board + power supply (5V 2.3A charger) (measured at the connection of the battery with the board - when turning on the power the value rises to 3.94V
none of the values change when you try to turn on the device
none of the elements on the board heat up excessively,
reading similar cases I thought it was a battery but I think the voltage on the battery is sufficient,
changing the value at power on probably also excludes the tape from the microUSB socket to the motherboard
I'm not sure if the screen fell (the question is how can I verify it)
or rather something with power supply and more on the board in one word what (and how) I can still verify to find out why the device has changed the cutting board? in the attachment gutters of the device (so that someone can tell what else to measure)

thanks in advance for every possible hint

Unfortunately, this type of equipment is not repairable by someone who does not have much knowledge and great manual skills. Replacing or even measuring something on this disc without a microscope is quite a challenge. The only thing you can do is check all connectors, if that doesn't help, look for a donor with a broken screen and change the disc. You can also take it to the website .

Maybe I will ask differently, how to check if the screen is working?
(assuming that I have a problem with the disc and without access to another - functional device)

You can make a controller for such a screen on fpga - there was a project on the forum somewhere, only expensive fun and considerable costs . Unfortunately, this cannot be checked with a multimeter, but usually faults do not occur in packages *, so sometimes it's worth the risk. (* - does not apply to devices made for sale from broken parts only).

And can a damaged charging module cause the tablet to not turn on at all? Hard, soft resets and other miracles do not help. The battery is charged and shows 3.7V