Taking bread as an example:
Homemade bread: flour, water, yeast, salt, maybe oil/butter depending on type.
A cheap white Tesco loaf in packaging: Wheat Flour [Wheat Flour, Calcium Carbonate, Iron, Niacin, Thiamin], Water, Yeast, Salt, Preservative (Calcium Propionate), Soya Flour, Spirit Vinegar, Emulsifier (Mono- and Diacetyl Tartaric Acid Esters of Mono- and Diglycerides of Fatty Acids), Rapeseed Oil, Flour Treatment Agent (Ascorbic Acid).
White loaf from the bakery department: Wheat Flour [Wheat Flour, Calcium Carbonate, Iron, Niacin, Thiamin], Water, Yeast, Wheat Fibre, Rapeseed Oil, Salt, Emulsifiers (Mono- and Diglycerides of Fatty Acids, Mono- and Diacetyl Tartaric Acid Esters of Mono- and Diglycerides of Fatty Acids), Flour Treatment Agent (Ascorbic Acid), Palm Oil, Preservatives (Acetic Acid, Calcium Propionate), Acidity Regulator (Sodium Hydroxide)
Jason’s (expensive) brand: Wheat Flour (Wheat Flour, Calcium Carbonate, Iron, Niacin, Thiamin), Water, Mixed Seeds (Golden Linseeds, Sunflower Seeds)(6%), Sprouted Spelt (Wheat) Grains (1.5%), Salt, Fermented Wheat Flour
These are the problematic parts and most of which generally fall into the UPF category on most scales: Emulsifiers (Mono- and Diglycerides of Fatty Acids, Mono- and Diacetyl Tartaric Acid Esters of Mono- and Diglycerides of Fatty Acids), Flour Treatment Agent (Ascorbic Acid), Palm Oil, Preservatives (Acetic Acid, Calcium Propionate), Acidity Regulator (Sodium Hydroxide)
So you can get packaged bread that is non-UPF (Jason’s in the above examples) and non-packaged bread that is UPF. If you want to avoid UPF you just have to become a label nerd and one of those annoying people standing in supermarkets reading labels on stuff.