Preheat an oven to 375 degrees F (190 degrees C). Grease 16 muffin cups or line with paper muffin liners.
Combine 1/4 cup flour, the cinnamon, 1 tablespoon sugar, the coconut, and 1 pinch of salt in a small bowl. Mix in 2 tablespoons of butter until completely incorporated into the flour; set aside.
Beat the unsalted butter, 1 1/4 cups sugar, and 1/2 teaspoon of salt with an electric mixer in a large bowl until smooth. Beat the first egg into the butter until completely blended before adding the second; continue mixing until light and fluffy. Combine 1 3/4 cups of flour with the baking powder. Stir into the butter mixture alternately with the buttermilk. Toss the blueberries with 1/4 cup of flour; stir into the batter along with the mango. Scoop the batter into the prepared muffin tins; sprinkle with the coconut streusel.
Bake in the preheated oven until golden and the tops spring back when lightly pressed, 25 to 35 minutes.