Under One Rule Origin *Spoilers!*

[Brodosaurus]

I bit disappointing. I was hoping they made ways to affect it by either limiting egalitarian support or maybe high stability.

Democratic Tendencies should not appear on planets with 0 egalitarian pops, so that should decrease the rebel strength. If they do, please report it

But the event will always fire, with the outcome based on your take on the issue and how the empire functions. If you are fairly good with your people, they should propose mediocre changes (and turn the empire to dictatorial always, which is actually a bug - it should depend on how bad you were towards them, if you treated people fairly then they should leave you as an Imperial even when you accept their demands).

 

[Brodosaurus]

Ah, so it's bugs, then.

Well, it depends on which part. The event will always fire up. If you have 0 egalitarians it will fire up too, but the modifier should be only on one planet.
Though, by getting added to the planet, it will make some egalitarians.