If it won’t even POST that sounds like mobo or psu.As said, I would try plugging in onboard video in case its something specific that’s failed related to the card slot. The video card may be ok I would think, but no way to tell as it is at the moment.
There is a chance this is the psu, and in dying wasn’t providing enough power for the gpu, and now has totally died. I assume there are no signs of power at all?
1-try onboard video
2-got an old psu? any size will do, just leave on onboard video
That would at least narrow down the mobo or psu question.