Place blueberries, lemon juice, zest, maple syrup and water in a medium saucepan over medium high heat, simmer until sauce thickens, stirring occasionally.
In a large skillet over medium high heat, place the sliced plums, sprinkle the cinnamon and nutmeg over the plums, add in the maple syrup and 1/2 cup of water. Allow to simmer, stirring occasionally adding in more of the water as needed to prevent the plums from sticking.
When plums have formed a sauce and starts to thicken add in the blueberry sauce and vanilla, reduce to a low simmer and allow to cook an additional 5 to 7 minutes.
While the sauce is simmering, place almonds and sea salt in bowl of food processor, pulse into course pieces.
Add in the dates and vanilla and pulse until combined.
Add the oats to the mixture and pulse until coarse crumbs are formed.
Transfer sauce to a serving dish and sprinkle crumble over sauce using your fingers.