Turn on a multi-cooker (such as Instant Pot) and the select Saute function. Melt butter in the pot. Saute onion, apple, and celery until onion and celery are slightly translucent, about 5 minutes. Add broth; scrape off bits from the bottom of the pot. Add gravy mix; stir until dissolved.

Combine kosher salt, thyme, rosemary, black pepper, sage, and garlic powder in a small bowl. Rub onto the turkey breast.

Lower a trivet into the pot; place seasoned turkey on top. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 50 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer's instructions, 10 to 40 minutes.

Mix water and quick-mixing flour together slowly in a bowl until slurry is smooth.

Unlock the lid and open the pot; transfer turkey to a plate. Strain the liquid from the pot; return it to the pot and select Saute function. Bring to a boil. Stir in the slurry slowly until gravy is thickened to your satisfaction. Slice turkey and serve with gravy.