In a large mixing bowl, combine the active sourdough starter, pumpkin puree, and lukewarm water. Stir until well mixed.
Add the bread flour, whole wheat flour, brown sugar, cinnamon, nutmeg, cloves, and ginger to the wet ingredients. Mix with a wooden spoon or your hands until a shaggy dough forms.
Add the salt and knead the dough in the bowl or on a lightly floured surface for about 8-10 minutes until the dough is smooth and elastic.
Place the dough in a lightly oiled bowl, cover with a damp cloth or plastic wrap, and let it rest at room temperature for 4 hours, performing a stretch and fold every hour to develop gluten.
After the bulk fermentation, shape the dough into a tight round loaf and place it seam-side up in a well-floured banneton or a bowl lined with a floured kitchen towel.
Cover the dough and refrigerate it for 4 hours or overnight for the final proof.
Preheat the oven to 450°F (230°C) with a Dutch oven or baking stone inside for at least 30 minutes.
Carefully transfer the dough onto a piece of parchment paper, score the top with a sharp knife or razor blade, and place it into the preheated Dutch oven or onto the baking stone.
Cover with the Dutch oven lid or a large metal bowl and bake for 20 minutes.
Remove the lid or cover and bake for another 25 minutes until the crust is deep golden brown and the loaf sounds hollow when tapped.
Remove the bread from the oven and cool completely on a wire rack before slicing.