Press Sauté and set the Instant Pot to Medium, Normal, or Custom 300°F. Set the time for 10 minutes, and press Start if needed. As the pot heats up, add the bacon to the inner pot of a 5-, 6-, 8-, or 10-quart Instant Pot. Cook, stirring often, until the bacon is browned, about 4 minutes. Use a slotted spoon to transfer the bacon pieces to a nearby plate.
Pour the broth into the inner pot and stir well to deglaze, scraping up the browned bits from the bottom. Add the potatoes and onion, then stir in the basil, salt, and thin red pepper sauce. Turn off the Sauté function and lock the lid onto the pot.
For MAX models only: Set the Instant Pot to Pressure Cook at Max level. Set the time for 10 minutes with the Keep Warm setting off. Press Start if needed.
For all other Instant Pots: Press Pressure Cook or Manual at High pressure. Ensure the pressure release valve is closed. Set the time for 12 minutes with the Keep Warm setting off. Press Start if needed.
When the pot has finished cooking, use the quick-release method to bring the pressure back to normal. Unlatch the lid and open the cooker. Press Sauté and set the Instant Pot to Medium, Normal, or Custom 300°F. Set the time for 5 minutes, and press Start if needed.
As the soup comes to a simmer, stir in the cream, milk, and instant mashed potato flakes. Stir constantly until the soup is slightly thickened and bubbling, which should take less than 1 minute.
Turn off the Sauté function and use hot pads or silicone baking mitts to transfer the (hot!) inner pot to a nearby wire rack to stop the cooking. Sprinkle the bacon bits and cheese over the top of the soup. Set the lid askew over the pot and let it sit for a couple of minutes to melt the cheese. Serve warm, garnished with minced scallions (green part only).