Okay, yes, I have to correct myself. I was under the impression the spheres of light representing Ultras in first episodes of some series (like original Ultraman, Ultraman Max, or the 2004 Ultraman movie) were the true form of the residents of the Land of Light, with the Ultra Armor simply being a suit they conjured up through energy to take a more physical form and make interactions with each other and other beings easier. This was supported by light particles escaping from wounds in some battles. The buildings in the Land of Light themselves looked quite energy-based to me, as well.
Reading up on it, it appears that the people of the Land of Light are in fact born with the Ultra Armor as a form of protective skin, and there seem to be instances suggesting even their bodies underneath the Armor is not entirely made of energy. There are also pictures from tie-in media (though apparently several decades old) showing the anatomy of Ultraman, Taro and Ultraseven, including organs and a skeleton:
OTOH, when Ultraman Jack lost his color timer during a fight, his energy left the Ultra Armor and seemingly left it like an empty suit:
I'm not sure what's been explicitly stated on-screen and what how much tie-in media like the anatomic images above are considered canon. But I'm pretty sure I remember wounded Ultras leaking light particles from cuts in their Armor, so at least partially they are beings of light.
Meanwhile, in this week's episode #20 of "Ultraman Chronicle Z: Heroes' Odyssey", Tiga has to confront an evil doppelganger: