Thaw the frozen spinach and squeeze out any excess water. Drain and chop the artichoke hearts. Soften the cream cheese by leaving it at room temperature for a while.
Set your Instant Pot to the "Sauté" function. Add minced garlic and sauté for about 1 minute until fragrant.
Turn off the "Sauté" function. Add the chopped spinach, chopped artichoke hearts, cream cheese, sour cream, mayonnaise, grated Parmesan cheese, shredded mozzarella cheese, grated Romano cheese, salt, black pepper, and red pepper flakes into the Instant Pot. Mix everything together until well combined.
Pour in the chicken or vegetable broth and stir it into the mixture.
Close the Instant Pot with the lid, ensuring the valve is set to "Sealing." Select the "Manual" or "Pressure Cook" function and set the timer for 5 minutes on high pressure.
Once the cooking time is complete, allow for a natural pressure release for about 5 minutes. Then, carefully turn the valve to "Venting" to release any remaining pressure.
Carefully open the Instant Pot, and your Spinach and Artichoke Dip should be hot, creamy, and ready to serve. Transfer it to a serving dish.