Heat oil in a large pot over low heat and cook onion and ginger until soft and translucent without browning onion, about 10 minutes. Add butternut squash and carrot; cook and stir, about 3 minutes. Add apple and cook for 2 minutes. Pour in broth, increase heat to medium, and bring to a boil. Reduce heat to low and simmer until vegetables are soft, about 20 minutes. Puree soup with an immersion blender until smooth.
Pour coconut milk into the soup and season with salt and pepper. Add lemon juice and maple syrup; stir until heated through, 2 to 3 minutes.