Preheat the oven to 275°F. Remove the thin membrane from the underside of the ribs (if present), then pat the ribs dry with paper towels.
Rub the ribs all over with the yellow mustard.
In a small bowl, combine the kosher salt, dark brown sugar, black pepper, garlic powder, onion powder, cumin, and smoked paprika. Then sprinkle the dry rub evenly over both sides of the ribs, pressing it in gently so it adheres.
Wrap the ribs tightly in a layer of parchment paper and then a layer of foil. Place them on a baking sheet or in a baking dish. Bake for 3–4 hours, or until the ribs reach approximately 195–205°F and are very tender, and the meat has pulled back from the bones. A knife should slide in easily, but the ribs should still hold together.
While the ribs bake, add the wild blueberries, brown sugar, fresh grated ginger, garlic, apple cider vinegar, gochujang, kosher salt, cinnamon, molasses, soy sauce, and smoked paprika to a medium saucepan over medium heat. Bring the mixture to a gentle simmer and cook for 15–20 minutes, stirring occasionally, until the blueberries have burst and the sauce has thickened slightly.
Remove the saucepan from the heat. Use an immersion blender to blend the sauce until smooth. If you don't have an immersion blender, carefully transfer the sauce to a blender and blend until smooth. Return the sauce to the saucepan if needed and simmer for another 2–3 minutes if you'd like it slightly thicker.
Remove the ribs from the oven and carefully open the foil. Transfer the ribs to a foil-lined baking sheet if needed. Brush the ribs generously with the blueberry BBQ sauce.
Broil the ribs uncovered for 3–4 minutes, or until the sauce is bubbling and lightly caramelized. Keep a close eye on them so the sauce doesn't burn.
To serve, brush with additional blueberry BBQ sauce, if desired. Slice between the bones and serve warm.