Preheat oven to 375°F (190°C). Combine ground turkey, garlic powder, paprika, 1/2 tsp salt, and 1/2 tsp black pepper in a skillet. Cook over medium heat until browned, then crumble into bite-sized pieces. Toss 2 cups shredded cabbage with 1 tbsp olive oil, 1/2 tsp salt, and 1/4 tsp black pepper. Divide cabbage between 4 bowls. Top each with cooked turkey crumble, cucumber, red onion, cherry tomatoes, and avocado. Drizzle with Greek yogurt mixed with Dijon mustard.