Currently, you cannot unlock the device (the one you are holding) using Termux because:
Unlocking the bootloader, whether via PC or Termux-assisted methods, carries serious consequences: unlock bootloader via termux
Two Android devices (Phone A – the target to unlock; Phone B – running Termux), USB-C OTG cable, and root on Phone B (optional but helpful). Currently, you cannot unlock the device (the one
Run the unlocker script. For Xiaomi, this involves retrieving a product token, running it through the script, and sending the mi-fastboot oem unlock command. whether via PC or Termux-assisted methods