In a large mixing bowl, whisk together flour, sugar, baking powder, salt, and cinnamon. In another bowl, mix milk, eggs, vanilla, and melted butter until well combined. Add the wet ingredients to the dry and stir just until combined — don’t overmix. Gently fold in the diced fresh peaches. Heat oil in a deep skillet or fryer to 350°F (175°C). Drop spoonfuls of batter into the hot oil, a few at a time. Don’t overcrowd the pan. Fry until golden brown and cooked through, about 2-3 minutes per side. Remove fritters with a slotted spoon and drain on paper towels. For the glaze, whisk powdered sugar, milk, and vanilla until smooth. Drizzle or dip warm fritters in glaze and let set slightly before serving.