@timofeyshhh Use the MiFlash tool to reinstall stock ROM and DO NOT lock the bootloader. There is a high chance of bricking the device if you so so. My Redmi Note 7 is my main UT device and it works really well on it.

@timofeyshhh Yes, you can reflash a different OS after flashing UT.

@MrT10001 thank you very much!