Place a 5- to 6-quart Dutch oven or heavy-bottomed pot over medium-high heat. Add the 1 tablespoon olive oil and heat until it shimmers.

Add the 1 1/2 pounds ground beef: Cook for 6–8 minutes, breaking it into small pieces with a wooden spoon, until no pink remains and the meat is well browned. If there is a large amount of rendered fat, carefully drain some, leaving a little in the pot for flavor.

Add the diced yellow onion and cook for 4–5 minutes, stirring occasionally, until softened and lightly golden. If the bottom of the pot begins to brown too quickly, reduce the heat to medium.

Stir in the 4 minced garlic cloves, 3 tablespoons chili powder, 2 teaspoons cumin, 1 teaspoon smoked paprika, 1 teaspoon oregano, 1 teaspoon kosher salt, and 1/2 teaspoon black pepper. Cook for 30–60 seconds, stirring constantly, until fragrant. Do not let the garlic or spices scorch.

Stir in the 15-ounce can pumpkin puree and the 28-ounce can diced tomatoes with their juices. Scrape the bottom of the pot with the spoon to loosen any browned bits.

Stir in the kidney beans, black beans, and 1 cup beef broth. The mixture should be thick but loose enough to stir easily. If it looks unusually thick, add a small splash of additional broth.

Bring the chili to a gentle boil, then reduce the heat to medium-low. Simmer uncovered for 35–40 minutes, stirring every 8–10 minutes to prevent sticking. The chili should become noticeably thicker, with the tomatoes breaking down and the surface gently bubbling.

Stir in the 1 tablespoon apple cider vinegar: Taste and adjust the salt, pepper, or chili seasoning if needed. If the chili is too thick, add broth a few tablespoons at a time. If it is too thin, simmer uncovered for another 5–10 minutes.

Ladle the pumpkin chili into bowls and top with shredded cheddar, sour cream, sliced green onions, or chopped cilantro, if using.