My understanding of ultra-processed would be things more like candy, cheetos, pringles, oreos, soda, etc.
It's hard to find a simple rule that isn't subverted. Though simpler more primitive diets (mostly low carb vegetables and high protein foods) seem best all around.
It's sad to see folks think they've leveled up enough to 'cheat' after loading up on yams ("veg!"), carrots ("veg"), and beans ("protein!").
All that said you can live without carbs and just digest fats instead. Hence the whole ketosis and low-sugar diets.
Probably Wonder Bread would look similar, but homemade bread quite different. All are processed foods of some level due to flour.
Cheerios seem surprisingly healthy (the first ingredient is whole grain oats and only 1g of added sugar). Even special K has 4g of added sugar per serving. I would consider sugar-coated cereal like raisin bran or special K with yogurt chunks ultra-processed.