"I played with a base recipe and came up with this to take to a friend's pool party. It was such a hit. All the guys said, 'Gosh, I didn't know anyone knew how to use a Dutch oven anymore!' I told them they were my guinea pigs because this was my first attempt with fresh peaches instead of canned. I don't think I can go back now; it was perfect, especially served warm with a scoop of vanilla ice cream. A little extra work but I can't wait to make it again."
Stir peaches, mango, rum, lemon zest, almond extract, 1/8 teaspoon cinnamon, and nutmeg together in a bowl.
Stir water, 1/2 cup white sugar, 1/2 cup stevia sugar substitute, and brown sugar substitute together in a pot; bring to a simmer. Stir peach mixture into pot; cook and stir until peaches are heated through, about 5 minutes. Remove from heat.
Whisk flour, 1/2 cup white sugar, 1/2 cup stevia sugar substitute, and a pinch of cinnamon together in a bowl; add milk and whisk to form a smooth batter.
Pour melted batter into the bottom of a Dutch oven. Pour batter over butter. Gently spread peach mixture with syrup on top of the batter.
Bake cobbler in the preheated oven until syrup is bubbling and crust is risen and golden brown, 50 to 55 minutes.