Solution is clear
"“As it is technically impossible for the user to have prior information about every data controller involved in a real-time bidding (RTB) scenario, programmatic trading, the area of fastest growth in digital advertising spend, would seem, at least prima facie, to be incompatible with consent under GDPR,” the IAB said."
So the IAB are themselves in agreement that real-time bidding is incompatible with GDPR. The solution is simple - no more real-time bidding. And if IAB and it's members lose business as a result... well, where did I leave my violin? I often mislay it, it's really small, possibly the world's smallest