They're not even just related to dinosaurs, they ARE dinosaurs.
My understanding is that there are differences between chickens and their predecessors, but that they're the closest we're going to get to their prehistoric relatives at present. They're a modern dinosaur, so to speak?
Yes, they are 100% modern dinosaurs. When I tell people that they sometimes don't think I'm being serious haha. While there are small variations between non-avian dinosaurs and avian dinosaurs (birds), the physical differences are minimal. Birds are also considered reptiles too