In a pressure cooker or rice cooker, turn on saute option and let it start to warm up while you gather your ingredients. Add oil and heat until shimmering.
Add onion, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook until softened, 3-5 minutes. add rice and cook, stirring frequently, until edges begin to turn translucent, about 2 minutes. Add garlic and oregano and cook until fragrant, about 30 seconds
Stir in broth and close lid and cook on rice setting with a rice cooker, or if using instapot, cook for 12 minutes on low pressure for white rice and 22 minutes on low pressure for brown rice. *see note
When done, and steam has released if using instapot, open lid and add chopped spinach, (see note) shut lid and let sit 5 minutes, uncover and fluff with a fork.
Stir in scallions, mint, and lemon juice, tossing until any clumps of spinach are broken up and thoroughly mixed into the rice. Season with salt and pepper to taste.
Transfer to a platter and sprinkle with feta cheese. Serve