Lenovo Legion 5 Y540-17IRH, blank internal display

[MicroSMD Lab]

Hi group, this laptop came in powering up but no display on either internal or HDMI. I cleaned ME of the bios (not sure if I did it properly, I followed SMDFlea's video guide but there was no file named "ME Region.bin but one named "ME Sub Partition.bin" so I used that name instead) and I get output on HDMI now.
The model name is 81Q4, board number NM-C531 Rev 2
Initially I got no +LCD_VDD voltage at the eDP connector but after testing U9 and U4406 I got 3.3V, no soldering or replacing components.
Now I get what I think is backlight (the logo lights up behind the screen) but still no image.
There is no sign of physical damage to the screen.
I don't have a test screen (unless a 40 pin screen from a dell G3 can work)
What are the voltages/ signals I should check to make sure that a screen replacement is the solution?

Sorry if I'm not to clear in what I'm asking.

[mcplslg123]

INVTPWM/BL_ON/19V nneds to be checked on edp connector. The name may vary as per schematics.

Clarify whether you've backlit now or not? Or is it no backlit but dimm display issue?

Link schematic/Bdv

[MicroSMD Lab]

Thanks you for taking the time to help me out.
I'm not getting backlight, there seems to be a separate logo light voltage.

+LCD_VDD = 20V
+LED_VDD = 3.3V
BFOFF# = 0V
MUX_INVT_PWM = 0V
EDP_HPD = 0V

I am not seeing any image when I shine a light
I also checked BL_PWM and BL_EN on the panel and both are 0V

Lenovo Legion Y540-17IRH Boardviewer - Badcaps

[mcplslg123]

MUX_INVT_PWM is at 0 Volt perhaps indicating GPU is not initialised .Check U4408/4409/4410 pin 4 voltage after pressing power button.

[MicroSMD Lab]

I got a 15" Legion Y540 and used that screen to test the motherboard and it works. It could still be the display cable because the location of the display connector on the motherboard has made it susceptible to corrosion and may have caused the display to go bad, one leg of the +LED_VDD line was eaten away. I will most likely add some sort of gasket (similar to those that dust proof the iPhone FPC connectors) as an improvement, I'm also open to suggestions.