24 hours before cooking, combine oats, water, and vinegar in a large bowl. Stir, cover, and let sit for 24 hours.
After 24 hours, dump oatmeal into a fine mesh strainer and rinse well, until the water runs mostly clear, 1-2 minutes.
Add the oats to the Instant Pot and add the dairy free milk and salt. Stir, put the lid on, and close the valve. Hit the "manual" button and reduce the time to 4 minutes. Once cooking is up, hit "cancel", release the pressure ad stir.
This is the point where you can add in a sweetener if desired. Serve right away or store in the fridge. It may look a little thin right after cooking, but it thickens up.