The screen is back.

But the replacement is on it's way.

Turns out, the backlight itself was ok - it's these little buggers are probably at fault here, which are LCD backlight step-up converters. Meet CPC2123ST-A2 and ACT6311UC.

They get their EN signals alright, they get their 5v in, but they refuse to step that voltage up and my assumption is that they were damaged when primary converter was releasing magic smoke.

Not gonna bother reversing that circuit, but i will say that for some reason output cascades of these fellas are in parallel and go out to the high side of LED backlight output.

A day ago i've ordered this "universal backlight replacement kit" that comes with long but thin PCB-based LED strip and it's corresponding driver circuit. So you can replace any backlight there is i guess.

Electrically wise it's almost a drop-in replacement, these scaler boards also have, apparently a connector for external backlight drivers which is hella neat:

Now all what's left is to cut the thing to thing's size and put thing into a thing to make it into a better thing:
Pack it up and boom, got my display back

It does not fit perfectly though, and power leads stick out and are not accomodated by screen holder, but i can move on for now and it's so bright i almost see how electrons escape this little IPS panel because of how hard that LED strip bombards it with light particles, forming this mysterious glow you usually see on nuclear reactor startup vids (it's probably camera lens fingerprint radiation).
But now this monitor proper requires both 12v and 5v, so i either need to stick to it's initial 12v only iteration, or move to other panel - but that will require another screen holder redesign.