Originally Posted by degeaba1981
I have the Chinese version of k20pro and now I'm running the eu version of rom that is saying that my redmi is a 9t pro.
I also tried to lock the bootloader with this rom, but the phone got stuck on bootloop.
I thought that my phone is bricked, as no unlocked bootloader, there is no possibility to install the twrp and mi flash gave me an error. Luckily I put the phone in fastboot mode and run again the process of unlocking the bootloader and worked for me.
I would like to give it another try, but when I will have more time to read what other steps are needed and not to end up with a bricked device, especially that I enjoy this phone a lot.
You can not lock the bootloader again if you have any ROM that is not for the same region as your phone. With a Chinese phone, this means you can only lock the bootloader when installing Chinese MIUI.
You were lucky you had already unlocked the phone before and so had unlock permission on your Mi account. Many others have bought phones with the bootloader already unlocked, then done the same as you. Because they could not then unlock the bootloader, they have ended up with a hard bricked device, which needed flashing with an authorised service account.