Hi! I've the same problem as some others with my Mi5 32GB, coming from a miui . it ROM (the latest one, 6.11.10).
Installed TWRP 3.0.2.3 with TWRP, rebooted (I checked the TWRP was correctly installed), wipe dalvik/cache/system and data for this nougat ROM.
Flashed with the error "E: unknown...