Thinly slice the fruit and mix together with maple syrup, nutmeg, and cinnamon. Lightly grease a casserole dish (I used olive oil, but you could probably skip this), and pour the mixed filling into the dish.
Bake covered on 350ºF for 30 minutes.
For the Streusel Topping:
Combine all of the ingredients for the topping in a large bowl and mix well. If using cool coconut oil or butter, you should melt it first.
After 30 minutes, remove the crumble from the oven and spread the topping over it. Return to oven and bake 20 minutes more.