How to get a trigger value?

I have set up a HomaAssistant MQTT integration working with the Nuki 4 Pro lock and it works fine, I guess.
Now I want to create a Node Red flow and for that I have to be able to distinguish if the lock has been operated from the outside (app) or from the inside (button). Lock state sent to Node Red listener doesn’t provide a trigger value, for now I’ve created a workaround and send a HTTP request to the web API but it’s not reliable (and it doesn’t seem elegant).
Reading the documentation I can see the “trigger” key, however I don’t see it in the messages I receive from the lock. What am I doing wrong?