In a small bowl, combine the smoked paprika, garlic powder, onion powder, cayenne, thyme, oregano, sea salt, and black pepper.
Pat the catfish fillets dry with a paper towel and coat both sides generously with the blackening spice mixture.
Heat the avocado oil in a cast-iron skillet over medium-high heat until the oil is shimmering.
Place the catfish in the skillet and sear for 3 to 4 minutes per side until the crust is dark and the fish flakes easily with a fork.
While the fish cooks, whisk together the Greek yogurt, Dijon mustard, hot sauce, lemon juice, and capers in a small bowl to make the remoulade.
Steam the green beans for 5 minutes until they are bright green and tender-crisp.
Serve the blackened catfish immediately with a dollop of remoulade and the steamed green beans on the side.