Heat oil in a large skillet over medium. Add onion, celery, and poblano, and cook, stirring often, until onion is translucent, about 5 minutes. Add garlic; cook, stirring constantly, until fragrant, about 1 minute. Add sausage; cook, stirring with a wooden spoon, until sausage crumbles and is no longer pink, about 3 minutes. Add rice, thyme, paprika, and cayenne; cook, stirring constantly, until fragrant, about 1 minute. Stir in stock, collard greens, salt, and black pepper. Bring to a boil; cover and reduce heat to low. Simmer until rice is tender, about 18 minutes.
Remove from heat, and let stand, covered, 5 minutes. Add scallions, and fluff with a fork to combine. Serve warm with hot sauce.