No Primary Culture Pops in States Fix
What does this do?
Adds 250 pops of your main primary culture to every state, in your empire where your primary culture makes up less than 0.1% of the population in order to make sure there is a cultural community for pops to assimilate into.
It does not affect the assimilation defines and should be compatible with pretty much everything.
The check is done yearly so it will not affect performance majorly.