Go to Mi Unlocker website and click on unlock now. Login into the website with your Xiaomi account credentials and submit your request. Then, you will receive a text message (takes 3 days to 21 days).

Upon successfully unlocking the bootloader of Xiaomi Mi 9 Lite, follow the steps below to install TWRP on Mi 9 Lite. Make sure to set-up ADB and Fastboot tools after downloading from the links ...