official source link to d/l OREO final
rename zip file to update.zip
copy to FAT32 formatted USB thumb drive
create a file WITHOUT EXTENSION including the following..
--update_package=/udisk/update.zip --wipe_data
(If not successful, remove --wipe_data and try again)
Save the file with name xiaomi_update (no extension) on thumb drive
Remove power plug from Mibox
press and hold BACK arrow and OK button (Do not touch any other buttons)
reconnect power
It should start recovery mode and automatically start update NO MENU SELECTION REQUIRED
If it starts showing colored dots, try again.
It may be useful to get an extra set of hands.....
For any of you who have yet to be targetted for Oreo.
Install via normal recovery