you never say "Quel un beau matin !"

Question

So how would one say "What a beatiful morning!"?

Also, this lesson addresses "What a...!" How do I say "how kind of you"?

Answer

Bonjour Johnny,
One way to say «how kind of you» is C'est trés gentil de votre part.  I am sure there are other ways which are better.

Answer

Bonjour Johnny !

To say "What a beautiful morning!", you will indeed omit the article "un" but keep the rest as is:
"Quel beau matin!"

As for "how kind of you" and such sentences, it's much trickier to express in French, as this structure simply doesn't exist.
Instead, you will use "Comme c'est gentil de votre part !" or "Comme vous êtes gentil !"

I hope that's helpful!
À bientôt !