TCL 55C803 Roku TV. Blank screen, but blacklight is on.

I have a 55 inch TCL 55Ç803 Roku TV that I found at someone's curbside for trash. The remote and power cord was included. The unit is very clean and no physical damage, so I optimistically brought out home for testing.

The TV powers on, lights up (but no image) and is dark with no lines etc. I can turn volume up and hear the familiar clicking of a the roku device imbedded, but no screen to navigate. Again can see the glow of the screen so assuming the LEDs are lit, but no menu images.

I've tried the well documented reset with the remote ” press home page button 5 times, 1 up arrow, 2rewind , 2 fast forward" and it then go through the reset process and turns TV off and on twice and ends up the same with the bottom tv indicator light flashing like several fast and a couple slow or something.

Again the screen is lighting up gray and can see it's lit up from inside. Seems a little darker on half the upper screen, but still lit up Any ideas?

I'm computer technical savvy, and would be comfortable taking it apart, but don't want to waste precious money trying to guess at replacing parts as I have no history on the TV and I realize it might exceed it's value to repair.

But I would sure love to fix it and use as I could not afford to buy such a nice TV.

Hoping this turns out to be a Thanksgiving blessing and gift for our family. Thanks in advance for any help.