am I correct that sheep and goats cannot be classified as glatt and certainly chicken cannot?
Sort of. The kula of the Rema, allowing a certain type of adhesion, doesn’t apply. However, the lungs most definitely do need to be smooth (chickens are assumed to be so without checking).
So as a matter of labeling, “glatt” is irrelevant, because if it’s kosher, it’s glatt. As a technical matter, lamb, veal, and fowl (I’ve never seen goat in the local grocery) is in fact glatt.