Heat 2 tablespoons oil in large saucepan on medium. Add onion and ¼ teaspoon salt and cook, covered, stirring occasionally, until tender and beginning to turn golden brown, 5 to 7 minutes. Stir in garlic and nutmeg and cook 1 minute.
Add rice and cook, stirring to coat, 3 min. Add wine and simmer, stirring occasionally, until nearly evaporated, 1 to 2 minutes. Add broth, 1½ teaspoons salt and ½ teaspoon pepper and bring to a boil. Reduce heat and simmer, covered, until liquid is nearly absorbed and rice is tender, 18 to 20 minutes.
Meanwhile, heat remaining 2 tablespoons oil in medium skillet on medium. When oil is hot, add sage and cook, stirring often, until crisp, 1 to 2 minutes. Transfer sage to paper towel–lined plate.
Stir pumpkin puree and nutritional yeast into risotto to combine and warm through. Serve topped with crispy sage and cracked pepper if desired.