Google's Noto project has a decent sans-serif Mongolian script typeface (https://www.google.com/get/noto/#sans-mong https://www.google.com/get/noto/#sans-mong)

Google's Noto project has a decent sans-serif Mongolian script typeface (https://www.google.com/get/noto/#sans-mong https://www.google.com/get/noto/#sans-mong) that is pre-installed on newer Android and iOS devices.