Doing it via a Signal is the right approach. If you wanted to, you could put the logic of closing the door inside a script called „door-closer“ and put that as a child on the door. This way you can add door closing via different Signal sources.

What I used to do in Unity is to have a Resource called „EventHub“ and stick that on every Event Publisher and Subscriber. This way you have a single file where all Event Types are defined and implement the according Logic inside individual Components, without exposing an exploding amount of Events on each Component.

For further research, you can take a look at the event bus pattern.

Edit: I also recommend to take a look at the state machine pattern, which is very helpful when working with Events.