Got LENOVO LEGION 5 15ITH6H , motherboard NM-D711.
Problem was blown mosfet on Discrete GPU memory power rail and shorted controller uP1666Q, replaced damaged components, but no picture, no initialization.
Found modified BIOS where integrated GPU is selected by default in BIOS, and got picture. So problem is with Discrete graphics, but laptop is still usable with iGPU. Just don't set BIOS to Discrete.
You can try BIOS attached, worked for me....