Xiaomi Chinese handset manufacturer has started rolling out miui 9 to some selected devices starting from xiaomi redmi note 4 and Mi max 2. They already made it official that the MIUI 9 will be made available on OTA. But, you can actually install it manually on your device if the need arises.
>>Open Miflash tools then select clean all in the right down corner >>Cick Select and browse to a folder where you extracted the Fastboot ROM and click Flash >>It will start flashing the phone and will take around 3-5 Minutes depending on the PC and device. Source