Is the gpu driver the same as before ?
You have the same os version as before right ? I suspect then it's indeed the motherboard. Not necessarily the mobo is "bad" but probably you have to find the right os version that is "compatible" with your new mobo. I have a hunch windows 10 versions are not necessarily good or bad per se but could be good or bad according to what mobo you have.
Personally, on my current laptop, windows 10 2004 is very bad but 20h2 is better and older versions are also better. I suggest you try older versions.