First of all, never USE both GPU and CPU in your CUDA options, uncheck CPU and leave GPU as being checked one.
As for your main question, believe it or not, but I’m too having GTX 1060 6GB and my Denoise node in Compositing works just fine (tested in 2.93 & 3.5.0)
I think the problem is that you have checked the CPU in your preferences
I’ve heard that it’s not affects your render time using both of these features enabled. It is rather to use something which more powerful than the other, in your case, I can assume, it is a GPU.
Check the answer from Thomas Dinges out there:
Seems like it’s possbile to do only with denoising being turned off