@randomredmi9a Remove the power cable and press the buttons (Volume Down + Power) to get to the bootloader (fastboot). It may just be a blank screen, but you should a feel the vibration and the screen will illuminate.
Before doing this download the latest MiFlash tool.
Download the correct Android ROM for the device.
Connect to the PC and use the MiFlash tool to flash the Android ROM to the device. In the bottom left corner of the MiFlash tool is a button that defaults to locking the bootloader. My advice - DO NOT RELOCK THE BOOTLOADER. This may (i.e. is highly likely) to totally brick your device.
Once you have installed Android and set it up, try installing UT again.
I have used this method a few times on boot looping Xiaomi devices and it has worked.
When you install UT to the device, be very patient, it may take some time to do things ~15-20minutes, so leave it alone.
Things you need:
Windows PC - Miflash tool doesn't work on Linux
MiFlash Tool
I don't know which country you are in to point you in the direction of ROMs