It is a hybrid ROM. It can be installed in TWRP or fastboot.
Installing with Fastboot:
Download Xiaomi.eu ROM zip file
Extract the ROM zip to a new folder
Power off your device
Boot your device in Fastboot mode (Hold volume down + power buttons)
Connect to PC via USB cable
Run one of the installation scripts (according to your PC operating system):
- install_and_format_data (or first_install_with_data_format) - with data wipe, if you're flashing Xiaomi.eu ROM for the first time or downgrading.
- install_upgrade (or update_rom) - without data wipe, if you're updating from an older Xiaomi.eu ROM.