Any Primitive can be Infiltrated 3.7+
Updated version from the Any Primitive Can be Infiltrated mod, here https://steamcommunity.com/sharedfiles/filedetails/?id=1947346617
Allows you to infiltrate the government from primitive civilizations at any time in their history (except post-apocalipse, due to limitations). Also strenghtens the effect of the Advance Knowledge mission results, so that a perfect result will always advance the primitives to the next level.
Warning: I have only tested this with the First Contact DLC, I have no idea if it works without it.