is there a way to get the Prefabs inside the NetworkManager NetworkPrefabs? Or at least the GlobalHashCode?
It seems kinda weird to create an extra Array/List that holds the Prefabs that already are declared inside the NetworkManager, just to spawn/instantiate an NetworkObject.
A couple years late, but I was just looking for a way to do this programmatically, and found a possible answer after some digging - perhaps it will help the next poor developer going down this rabbit hole.
var somePrefab = networkManager.NetworkConfig.Prefabs.NetworkPrefabsLists[0].PrefabList[0];
This assumes that networkManager is pointing to your NetworkManager.Singleton, and that you have created and assigned a NetworkPrefabList with NetworkPrefabs to the manager in the editor.
It is simply an example to show the reference chain - which seems to indicate that the network prefabs lists are stored in a list of lists, which is stored in a wrapper, which is stored in the NetworkConfig which is referenced in the NetworkManager.
Some ideas to simplify this could be to extend the NetworkManager and have a direct reference, and even extend the NetworkPrefabList SO to contain keep a dictionary or something to allow for quick lookups.