Add the broth, Greek yogurt, mayonnaise, onion powder, garlic salt, black pepper, spinach, artichokes, and cream cheese to the Instant Pot insert.
Lock the lid and turn the valve to Sealing.
Set to High Pressure for 7 minutes.
When the timer ends, carefully do a quick release by turning the valve to venting.
Open the lid and stir well.
Stir in the Parmesan and mozzarella until melted and smooth.
(Optional) For a golden top, transfer to an oven-safe dish and broil 3–5 minutes.
Serve warm with chips, bread, crackers, or vegetables.