Place the potatoes in a medium saucepan and add enough water to cover them by about an inch. Add a generous pinch of salt and bring to a boil over medium-high heat. Reduce the heat to medium and simmer for 5 minutes until they can be poked with a paring knife with some resistance. Drain the potatoes well.
In a large cast-iron skillet, cook the bacon over medium heat, stirring frequently, until crisp, 5 to 7 minutes. Use a slotted spoon to remove the bacon to a paper towel-lined plate, reserving the drippings in the pan. Add the oil, bell pepper, and onion to the drippings in the skillet and cook over medium heat, stirring, until the vegetables start to soften, 3 to 5 minutes. Add the potatoes, chili powder, cumin, garlic powder, black pepper, and 2 teaspoons salt and stir to combine. Cook, flipping the potatoes occasionally, until golden brown, crisp, and cooked through, 8 to 10 minutes. Drizzle with the barbecue sauce, then sprinkle with the cheese, jalapeños, bacon, and green onions. Serve with sour cream.
