Text changes when there are no entities around

I have a quest system that says to defeat the remaining rebels. I want it so that when there are 0 rebels left within a certain distance change the quest text, how would I approach this?

I would start to try with a collision component or a Line trace to detect the ennemies then the rest is pretty simple, if it detect one, don’t change the text, etc… There is probably other simple method to do that, but that’s the two I used for similar situations.