Press Sauté and add the olive oil, onion, garlic, turkey, and 1 teaspoon salt to the Instant Pot. Sauté until the turkey is browned and cooked through, breaking it up with a wooden spoon as you stir, about 8 minutes. While the meat is cooking, pour the diced tomatoes, with their juices, into a blender and blend until smooth. Set aside until the meat is browned.
Press Cancel to change cooking cycles. Add in the blended tomatoes, celery, carrots, vinegar, maple syrup, oregano, basil, and 1/2 teaspoon salt and stir well.
Wash the spaghetti squash and carefully pierce the skin with a sharp knife to vent. Place the whole squash directly into the sauce, making sure that the area where you pierced the skin is facing up, out of the sauce, to vent. Secure the lid and move the steam release valve to Sealing. Select Manual/Pressure Cook to cook on high pressure for 15 minutes.
When the cooking cycle is complete, let the pressure naturally release for 10 minutes, then move the steam release valve to Venting to release any remaining pressure. When the floating valve drops, remove the lid. Use oven mitts to lift the spaghetti squash out of the pot. Transfer it to a cutting board to cool slightly. Stir the coconut milk into the sauce and season with salt and pepper, to taste.
Cut the cooked spaghetti squash in half crosswise, and use a spoon to remove the seeds from the center. Use a fork to scrape out “noodles” from the squash and place them on plates. Spoon the Bolognese sauce on top of the noodles and serve. Store leftovers in an airtight container in the fridge for 1 week.