I had the same request and I got this suggestion
that is similar to what was described here, but the point the author of the post makes is the fact that you need to add you artist to the library and then ban it. It is a counter intuitive process and has the problem that you keep adding artists that you don’t like to your library just to be able to ban it.
As much this can work I would love to see a better way to manage this problem
thanks
M