Heat the oven to 400 °F. Prick the sweet potatoes all over with a fork, rub them with the olive oil, and set them on a parchment-lined sheet pan. Bake 45-50 minutes, until a knife slides into the center with no resistance.
While the potatoes bake, combine the black beans, corn, salsa, cumin, smoked paprika, and salt in a small saucepan over medium heat. Simmer 3-4 minutes, stirring, until hot; add a splash of water if the mixture looks dry.
Let the potatoes cool 5 minutes, then split each one lengthwise and fluff the flesh with a fork.
Spoon the warm black bean mixture into the potatoes.
Top with Greek yogurt, avocado, and cilantro, and serve with lime wedges.