Just to share my today's story here.
I updated the mi 8 rom from 8.10.12 to 8.10.18 then the phone bricked!
Finally I fixed my mi8 after paid CNY 160 to chinese xiaomi professional to have an official account to flash.
the reason which caused the black brick was that the downloaded file was...
Hello everyone
the current xiaomi.eu for MI8 i am using have a high battery usage on Cell standby which is about the level of Screen usage.
I input *#*#4636#*#* on the dial found out the network had been set LTE/TD-SCDMA/UMTS.
Because there is no TD-SCDMA signal beside the mainland of China...