Buying Pop Under Traffic

Does anyone buy pop unders traffic to promote affiliate offers? If yes for what niche?
I tried once to buy traffic on https://www.popads.net/ to promote smart links from mobipium
But couldn’t get profitable in my trials
I wonder if anyone here works with paid campaigns and could share some guidelines on how to get a profitable campaign with pop traffic

thank you

It is usually garbage bot traffic that you will get from these networks…