Preheat the oven to 400F. Line a muffin tray with 16 paper liners.
Whisk together the all-purpose flour, brown sugar, baking powder, salt, baking soda, cinnamon, and nutmeg in a large bowl.
Add the milk and vinegar to a medium bowl and let it sit for 3 minutes without stirring so the milk can curdle. Whisk in the eggs, oil, and vanilla.
Stir the wet ingredients into the dry, being careful not to over-mix, and then fold in the diced peach.
Divide the batter between the 16 muffin wells and sprinkle on the crumble topping.
Bake until a toothpick inserted in the center of a muffin comes out clean or with just a couple crumbs, about 15 to 20 minutes.