Looks like right now there are no natinal burgers in menu. I searched pictures and found those:
1) "Ukrainian Burger" with rue bread, chicken and bacon. Not sure what's so "Ukrainian" about that one, seems like a normal smallish burger, but who knows.
2) Some "Ukrainian menu". Again, rue bread, bacon, fried onions.
I guess they call everything Ukrainian national if it has pork and rue dark bread.
But again, they are all seasonal and new ones seem to appear every now and then. Here is the current menu: https://www.mcdonalds.com/ua/uk-ua/eat/fullmenu/burgers-and-rolls.html
But the site does not seem to have language switch, so only Ukrainian.