Which method did you use to unlock bootloader. Worthwhile requesting from Mi? Turnaround time?
I requested the code,it seemed to get stuck at 50%.Apparently that's been fixed recently.
I used the unofficial method of replacing the recovery image with TWRP
Extract MiUi 8 Global Developer ROM and replace recovery.img (in images folder) with ZCX TWRP's recovery.img
Flash using Mi Flash (in EDL mode) and check clean_all
After finished flashing process unplug and press [volume up]+[power] until Mi logo shows up then release buttons and it boots to TWRP (change TWRP language from chinese to english: click here)
Reboot to system and accept that TWRP disables/overwrites standard recovery
Boot to MIUI and complete initial setup (important step)
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Shutdown device and boot to TWRP again
Perform factory reset and wipe system
Flash Psy_man's latest firmware, LineageOS 14.1 and GApps (ARM64, Android 7.1)
Wipe Cache, Dalvik
Reboot to system and you're DONE!!