-You may use milk in the place of buttermilk, the result will not be quite the same, but will work. If you have sour cream or 1/3 cup of yogurt, you may use that in place of buttermilk.
-Fresh peaches vary in degree of juiciness. If your peaches are very juicy, place them in a bowl and mix with 2 teaspoons of sugar. Toss and let the peaches macerate for about 15 minutes. Drain the juice off of the fruit (discard juice) and use fruit in recipe. This process with extract some of the excess juice off of the fruit so the muffin will not become soggy!
-Frozen peaches work well in this recipe. Do not thaw before using, just chop the frozen fruit. I have also used frozen pineapple (3/4 cup along with 3/4 cup of frozen peaches) with great results! I actually prefer 1/2 pineapple and 1/2 peaches. I have not tested canned peaches or canned pineapple or fresh pineapple in this recipe.
-Coconut oil may be used in place of the butter in the muffins, but not in the streusel. I like the flavor of coconut oil in muffins, but the structure of the muffin will be less stable than if using butter.