Bring a large pot of salted water to boil; keep warm.
Heat olive oil over medium heat in a large, deep pot. Add chicken and sauté until brown, about 1 minute. Remove to a plate. Add onion, eggplant, garlic powder, and oregano to pot; sauté until brown and eggplant is crusty, about 15 minutes. Stir in artichokes, if using. Reduce heat and keep warm.
Return salted water to a gentle boil and add potatoes. Cook for 8 minutes, and then add green beans; cook for 1 minute, and add pasta. Cook until pasta is al dente and vegetables are tender, 8–10 minutes. Drain, reserving 1 cup pasta water.
Increase onion-eggplant mixture to high heat. Add pasta water and pesto. Boil until liquid is reduced by half, 3–5 minutes. Add chicken, pasta, green beans, and potatoes. Toss well and heat through, squeeze lemon juice over all, and serve.