Every dog I’ve ever had, including the current, “hungriest” dog on the planet (she’ll eat anything, including non-edible things like the couch stuffing, and is on a perpetual diet), have refused to eat them. Picky dogs, not picky dogs…doesn’t matter, they apparently don’t consider hard cooked egg whites to be food.
They have an odd texture, have no smell, have little taste, but they are food! I eat them, but, nope, no dog I’ve ever known is having it. They’ll take a boiled egg apart and eat the yoke, but the white is always carefully left alone.