XiaomiToolV2

Try this one: https://github.com/topminipie/XiaoMiToolV2

Or This: https://androidmtk.com/xiaomitool-v2

Solution

https://github.com/topminipie/awesome-xiaomi-bootloader-unlock#miunlocktool--mibypasstool--mitool

Download this: https://github.com/offici5l/MiUnlockTool

One device per Mi account per Month