Season chicken with salt, Cajun seasoning, paprika, black pepper, garlic powder, and onion powder; toss well and rest 10 minutes.
Heat oil in a large heavy pot over medium-high heat.
Brown sausage slices on both sides; remove and set aside.
Add chicken to the same pot and brown lightly for 4–5 minutes; remove and set aside.
Add onion, bell pepper, and celery to the pot; cook 5–7 minutes, scraping up browned bits.
Add garlic and cook 30 seconds until fragrant.
Return chicken and sausage to the pot and stir well.
Add thyme, oregano, bay leaves, and cayenne if using.
Pour in chicken broth and bring to a gentle boil.
Add dry pasta, stir well, cover, and simmer 12–15 minutes, stirring occasionally.
Cook until pasta is tender and most liquid is absorbed; add more broth if needed.
Remove bay leaves, adjust seasoning, and rest 5 minutes before serving.
Garnish with sliced green onions and serve hot.