Set Instant Pot to sauté, then add chopped bacon. Stirring occasionally, cook bacon until fat has rendered but not until bacon is crispy, about 3-4 minutes.
Once bacon is just cooked, add butter, onion, and celery. Cook until onion is soft and start to turn translucent, about 5-6 minutes, making sure to stir often and scrape up any browned bits that may be stuck to bottom of pot.
Add garlic, one large pinch salt, and black pepper. Cook for 1 additional minutes, stirring often.
Add potatoes and clam juice both from bottle and reserved juice from cans to mixture, and stir. Cancel Instant Pot sauté mode, add lid to pot and lock in place. Turn steam release knob to sealing position.
Set Instant Pot to manual high pressure for 4 minutes. Once time is up, let natural release for 5 minutes, then finish with quick mode until steam is fully evaporated.
In medium bowl, whisk together all-purpose flour and half and half until smooth. Open pot and stir in mixture into soup. Set Instant Pot back to sauté mode, and continue cooking soup uncovered, stirring often, until thickened, about 6 to 8 minutes.
Add in minced clams, heat through for few minutes without bringing chowder to boil. Add in salt and black pepper, and vinegar if desired. Sprinkle with fresh chopped chives, and serve warm with oyster crackers or baguette.