Add the ground beef, potatoes, celery, carrots, and chicken broth to the Instant Pot. Cover, turn the knob to seal, and cook on high pressure for 15 minutes. Let the pressure release for ten minutes, then quick release.
While the pressure is releasing, melt the butter in a medium saucepan over medium heat. Stir in the flour. Cook 3-4 minutes, or until golden brown. Slowly stir in the milk, a little at a time, while whisking constantly. Cook 3-4 minutes, or until thickened. Remove from heat, then stir in the salt, pepper, garlic powder, and cheddar cheese.
Pour the cheese sauce mixture into the Instant Pot and stir to combine. Cover and cook using the slow cooker function for an additional 15-20 minutes.