Salt Vinegar Potato Soup

Name: Salt & Vinegar Potato Soup
Ingredients: 1 large yellow onion; 4 large stalks celery; 3 cloves garlic; 1/2 cup plus 3 tablespoons olive or vegetable oil, divided; 2 1/4 teaspoons kosher salt, divided, plus more as needed; 3/4 teaspoon freshly ground black pepper, divided; 2 pounds Yukon Gold potatoes (about 5 large); 2 (about 15-ounce) cans white beans, such as cannellini or navy; 1 (about 13-ounce) can full-fat coconut milk; 1/2 teaspoon red pepper flakes (optional); 1/4 cup distilled white vinegar, plus more as needed; Coarsely chopped fresh dill, for serving (optional)