I have the exact same issue. I just upgraded from my 4790k and z97 to a 5950x and x570 unify. I was using my new 3080 since November with no audible levels of whine. Now a few days ago, with my new cpu and the same GPU, I get a terrible whining noise when playing stuff like assasin's creed odyssey. Furmark and aida64 didn't make much noise at all.
I'm at a loss frankly and its annoying enough that it sounds like something is horribly wrong with the machine. Almost sounds like a pump failing.