Please note that in order to unlock the bootloader of the Realme GT 2 Pro, you will first need to put an unlocking request in a device-specific unlock app named “In-Depth Test”.

Xiaomi already rolled out MIUI 12 closed beta builds for several smartphones. Here you can find the download files for your compatible deve.

You can manually sideload the firmware on your device if you wish to, but it requires an unlocked bootloader, which is a time-consuming process on Xiaomi phones.