Cut lemon in half; cut one half into thin slices and set aside. Zest and juice the remaining lemon half into a 1-gallon resealable plastic bag. Add 3 tablespoons olive oil, 1 clove minced garlic, 1/2 teaspoon Greek seasoning, and salt to the bag and seal. Move ingredients around in the bag, gently pressing, to mix.

Add shrimp to the bag, reseal, and gently move shrimp inside the bag to coat with marinade. Try to get as much air as possible out of the bag, reseal, and place on a plate. Move shrimp into a single layer inside the bag, and refrigerate shrimp in the marinade. Turn occasionally.

In a Dutch oven, heat remaining 2 tablespoons olive oil over medium heat.

When oil shimmers, add onions, bell peppers, and rice. Cook, stirring, 3 to 5 minutes, or until the onion begins to turn clear and the rice begins to toast. Add remaining 2 cloves garlic and red pepper flakes. Cook, stirring, until garlic is fragrant, about 30 seconds.

Add diced tomatoes and their juices; pour in chicken broth and wine. Stir in parsley, red pepper flakes, and remaining 1 teaspoon Greek seasoning, and bring to a boil. Cover, reduce heat to low and cook until rice is tender with a bite, 15 to 20 minutes. Season to taste with salt.

Increase heat to medium; stir in shrimp and marinade. Bring to a boil; stir in spinach and artichoke hearts. Cook covered, stirring occasionally, until shrimp is pink and opaque and rice is tender, 5 to 8 minutes.

Sprinkle with Parmesan, garnish with parsley sprigs, and serve with lemon slices.