Heat the olive oil in a large Dutch oven over medium heat. Add the onion and bell pepper; cook until softened and the onion is translucent, about 5 minutes.

Add the garlic, chili powder, cumin, smoked paprika, and oregano; cook, stirring constantly, until fragrant and the spices darken slightly, about 1–2 minutes. Don't let the garlic burn.

Stir in the pumpkin puree until it coats the vegetables — it will look pasty at first, then loosen as the tomatoes go in. Add the fire-roasted crushed tomatoes and the vegetable broth, scraping up any browned bits.

Stir in the black beans, kidney beans, brown sugar (if using), salt, and pepper. Bring to a lively simmer, then reduce the heat to medium-low and cook, partially covered, 15 minutes, stirring occasionally. The pumpkin melts into the sauce as it simmers.

Mash about a cup of the chili against the side of the pot with the back of a spoon (or a quick 2–3 pulses with a potato masher) for a thicker body. Stir in the lime juice and taste — add more salt or a pinch of brown sugar if the tomatoes taste sharp.

Ladle into bowls and set out sour cream, cilantro, lime wedges, avocado, and cotija (if using) so everyone finishes their own.