How to override NetworkManager

Unity Engine
,
1

Is there a min version for 2021.3 (I have 2021.3.8f1) ?
I tried to override NetworkManager because I want to change a few things before spawning the player but I can’t find the method explained in the documentation.

I do :

public class CustomNetworkManager : NetworkManager {
        public virtual void OnServerAddPlayer(NetworkConnection conn,short playerControllerId) {
            print("TOTO");
        }
    }

But the function isn’t invoked nor found.
I took the code from here

2

I think I got the wrong documentation, the new documentation doesn’t talk about this snippet of code, I’ll look into it