Inside Dell T3600 with Xeon E5-2690 v1 (guess it's 3rd gen CPU in desktop realm) I have AMD RX 460 and P106-100. Three monitors are connected to RX card. Matlab and Python are using P106 for calculations without issues.
I have done all hacks suggested here, and now can open Nvidia control panel, but most of the games still ignore P106 and utilize RX 460.
There is still hope, I have tried to play DOTA 2 using Vulkan API and it automatically used P106 with impressive frame rates. When used in other API modes it defaults to RX card.
I will try to find some more Vulcan games, and report back.