Hi! If your model doesn’t have any bones for it’s facial expressions, you normally can’t animate them or even add control rigs using the engine since control rigs need bones to control. But it’s not over! You can enable the “Skeletal Mesh Editing Tools” plugin to add new bones to your mesh inside the engine, although I recommend the implementation of the bones in this case using a 3D editor.
Hey did I say bones? That can also be used to animate face but after my reply, I researched a bit more and remembered the existence of morph targets on the way so please don’t try to add bones instead of them in your 3D editor for facial expressions