Hello, you get the warning icon because when you create the linked mesh, it is automatically placed outside the skin placeholder so that is can be easier for you to move the beard linked mesh to the correct skin.
But the fact that this linked mesh is in no skin causes the warning icon to be displayed as long as not in a skin, because the bones it is supposed to be bound to are in a skin, and not active if no skin is active.
This is an easy fix: simply add the linked mesh back in the skin placeholder with the correct skin active, and make sure to also add the beard bones to it. You'll see the mesh is restored and the warning icon will also go away 😃
