Rinse the soybeans under cold water. Transfer to the Instant Pot liner. Cover with the water and close the lid. Set the valve to "Sealing."
Pressure cook for 40 minutes and let the pressure release naturally (about 25 minutes). Once there is no more pressure, open the Instant Pot and drain the cooked soybeans.
Transfer the cooked soybeans to a clean kitchen towel and let dry for 20 minutes. The soybeans should not be wet. If they still appear too wet, top them with another clean kitchen towel and press a bit to absorb excess water.
Transfer the soybeans to a large mixing bowl. Add the rice vinegar and stir using a wooden spoon. Sprinkle the tempeh starter and stir again until well combined.
Take two freezer bags and pierce them using a fork or a chopstick at 1-inch intervals. Divide the soybeans into the freezer bags and pack them well. Then fold the rest of the bag over the soybeans to keep it tight.
Wash the Instant Pot liner. Place 1 cup of water in the bottom and top with the steam rack. Place the two tempeh loaves on the steamer. Cover with a glass lid (or use the Instant Pot lid if you don't have a large glass lid).
Press the Yogurt button 3 times to set it to "Less" mode. Set the timer for 16 hours.
After 16 hours, turn off the Instant Pot. You should start to see some white mold appearing. Remove the excess water from the lid using a paper towel. Place the lid back into place and let the tempeh incubate for another 24 hours.
After 24 hours, the tempeh should be fully covered with white mold and bind the soybeans together into a firm cake. You can now place it in the refrigerator and use as you wish!
Tempeh will keep for up to 2 weeks in the refrigerator or 6 months in the freezer.
Notes
If you can't find split and peeled soybeans: Soak the whole soybeans overnight. The next morning, rinse and place in a large bowl. Cover with water. Using your hands, massage the beans to remove the hulls. Hulls will float on top, remove them using a colander and discard them. Then you can cook the soybeans and follow the recipe.