Pretty sure you didn't read my comment before you linked that
The 'Guide' that is posted here is exactly the same as that XDA thread. It's telling you how to installl MIUIv11, via the fastboot.bat that's inside the .zip
MIUIv12 that's in the OP here doesn't have anything like that, it just says install TWRP and go ahead.. How? there is no TWRP for the 9 Pro EU. That's my question, how am i supposed to install it then?
Edit: Not to mention.. the table states that there is support for it, however, in the download links there is no HMNote9ProEU, so there isn't even a ROM for it.