You'll get a few different opinions on how to tackle this and there's no 'one right answer'.
One way to do it is to override the voltage with a static settings and then adjusting LLC to let it 'give a little extra' when the CPU is under load.
You won't earn any points with the environmental team, and will probably spend a few dollars more per year on electricity, but setting it to something like a static 1.24v and allowing LLC to give some more may get it stable and within what your cooler can do for 10-15 mins.
As a side note, my system is not perfectly stable. Prime95, small FFT, eventually gets my i9-9900k above what I consider safe, but nothing else I run even comes close - so I'm okay with that.