Turn Instant Pot to the Sauté function. Once it says HOT, add the butter to melt.
Add the onion, carrot and celery and cook for about five minutes, stirring occasionally. Add the garlic, sugar, salt, ground thyme and cook for about one minute more, until the garlic is fragrant.
Add the ground sirloin and sauté until no longer pink, breaking up the beef as you sauté. Add the red wine and allow to cook for a couple of minutes, to cook off the alcohol content and leave behind the flavor.
Add the crushed tomatoes to the pot and stir well.
Turn the Sauté function off. With the lid set to "Sealing" put the lid on the Instant Pot.
Press the "Manual", "Pressure Cook" or "Soup/Broth" button (depending on the model of your Instant Pot) and press the down arrow, setting the timer for 15 minutes.
Allow the steam to natural release.
While the sauce is pressure cooking, boil the pasta and drain.
Taste the sauce. Add more salt if necessary. Serve the bolognese atop the spaghetti, topped with chopped parsley and Parmesan if desired.