Set a 6-quart Instant Pot® to Saute. Add the olive oil and wait until it gets hot. Add the sausage and cook, breaking up clumps with a wooden spoon, until brown, about 5 minutes. Remove sausage with a slotted spoon and transfer to a bowl. Add a splash of water and scrape up the brown bits, then discard. Wipe down the inside of the pot.
Stir together the ricotta, egg, oregano, nutmeg and 1/4 teaspoon salt.
Break the noodles into approximate thirds (it's okay if little shards break off too).
Spray a 7-inch round cake pan with nonstick spray.
Spread a little bit of sauce in the bottom of the pan, then top it with a layer of broken lasagna noodles so that they slightly overlap and cover most of the pan. Top with a third of the ricotta mixture and about a third of the mozzarella, then a sprinkle of Parmesan. Sprinkle a third of the sausage over the cheeses, then drizzle with 1 cup marinara sauce. Repeat 2 more times: noodles, ricotta, mozz, Parm, sausage, marinara. Top with one last layer of noodles, a thin layer of the remaining marinara, making sure not to cover completely with sauce, and then the remaining mozzarella. Sprinkle with the remaining Parmesan.
Create a sling for your pan by folding a 24-inch sheet of foil lengthwise twice place under the pan.
Place the trivet in the bottom of the Instant Pot® and add 1 cup water. Set the lasagna on the trivet, then cover the pot. Set the pot to Pressure Cook on high and set for 30 minutes. Manually release the valve when it is done.
Preheat the broiler.
Carefully remove the lasagna from the pot, and place on a sheet pan. Broil the lasagna in until bubbling and browned in spots, about 2 minutes. Let stand for 20 minutes before serving.