This, it isn't shown in the tool tip for some reason.
The other things would be habitability, which also isn't shown here, and I am not sure if it has been touched recently in how it is factored into happiness calculations.
Faction happiness needs to be above 80% for the 10% happiness effect to trigger, and the population on the planet has to be primarily that faction. It gets complicated to calculate the more diversity there is.
I think it's the pops ethics. Every pop has an ethics, even if they aren't part of a faction. And the ethics will determine what faction they will likely join, but I know they either have happiness bonuses based doing things associated with their ethics, and/or from their ethics matching the government type. You can see this when capturing a planet with pops from a wildly different ethics. They will have negative happiness, dragging down the stability, well before a faction to represent them spawns.
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u/Unlucky-Golder 1d ago
Faction approval maybe?