Preheat oven to 375 degrees. Prepare a muffin tin with paper liners or silicone baking cups. Set aside.
To a bowl, add the dry ingredients: flour, sweetener, baking powder and salt. Whisk together until combined.
In a separate bowl, combine the wet ingredients; almond milk, egg, oil and vanilla. Whisk together until combined. Gradually add the wet ingredients to the dry ingredients using a whisk to combine. Do your best to not overmix.
Using a rubber scraper, genty fold in the diced peaches.
Spoon the batter into the prepared muffin tin, filling each cup to about 3/4 full.
Struesel topping: in a bowl, combine the flour, brown sugar substitute and salt. Pour in the melted butter and mix together with a fork. Mixture will be crumbly and gravel-like. Top the batter of each muffin generously with the streusel crumble mixture.
Place muffins in oven and bake for 18-20 minutes. To test for doneness, insert a toothpick into the center of a muffin. If it comes out clean and crumb-free the muffins are done.
Let cool 10-15 minutes before enjoying.