How to get all actors of certain level instance (include itself) for dynamically loaded levelInstance

I tried to load a level instance by calling LoadLevelInstanceBySoftObjectPtr with C++. And I would like to collect the references of all actors inside the level instance for further use. But the following code snippet does not work as expected.

ULevel* Level = LevelStreamingDynamic->GetLoadedLevel();
if (Level)

{

    ActorList.Append(Level->Actors);

}

I could only get WorldDataLayers, world settings and level script actor here. It seems other actors are spawned at persistent level instead.

(My Engine Version is 5.4.4)