There's enough of a Ukrainian community in Lincoln that there's a Ukrainian church. I wonder if they make those breads for their weddings? The recipe I found uses two different doughs, a yeasted dough for the bread, which is split in two so that there's a center and a braided outer ring, plus a non-yeasted dough made with heavy cream for the decorations.
The one pictured in the Atlas Obscura article must use two different doughs for decoration, a light one and a darker one, I wonder if it is done with a rye flour or with some kind of coloration, like cocoa?