There are 2 repositories under unlock-bootloader topic.
Unlock Bootloader of any Device using PC or Android.
Awesome Xiaomi BootLoader Unlock
Installs a persistent backdoor binary on android devices with unlocked bootloader via TWRP that runs as system daemon with root permissions and without SELinux restrictions
BootLoader unlock tool for Xiaomi devices
Persistent backdoor for Android devices with unlocked bootloader. Runs as root in unrestricted SELinux context and can hide itself from anything except root