In a large bowl, combine blueberries, 2 tablespoon maple syrup, lemon juice and tapioca starch. Stir together until fully combined then transfer to a tart pan (or pie pan/baking pan).
Using the same bowl, mash the banana until smooth, trying to remove as many lumps as possible. Add in oats, spices, remaining maple syrup and coconut oil. Stir everything together until combined, then transfer the topping onto the blueberries, using your hands to spread it out evenly across the top.
Bake the crumble on the center rack for 40 - 45 minutes, covering for the last 10 minutes if needed. Blueberries should be bubbling and the oats should be golden brown.
Remove from the oven and let cool for 10 minutes before serving. Serve warm with ice cream, yogurt or coconut whipped cream!