Pour 1 cup water in a multi-functional pressure cooker (such as Instant Pot®) and place a steamer rack trivet in the bottom.
Stir together remaining 1 cup water, oats, milk, brown sugar, maple syrup, cinnamon, and salt in a heat-safe bowl. Place the bowl on the trivet.
Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 6 minutes. Allow 7 to 10 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, for 10 minutes. Release remaining pressure carefully using the quick-release method, about 5 minutes. Unlock and remove the lid.
Remove the bowl from the pressure cooker and stir. The oatmeal will thicken as it cools.