Same with me.. but im not sure why did not not start. maybe because i mesh when run a script on su folder.
Reflash with the same rom version xiaomi.eu_multi_HM2XTDPro_7.3.30_v8-5.1 rom dont choose to install supersu in TWRP after preparing because it wasnt boot for me too..
I clear cache in twrp to stop reflashing and optimizing everytime I boot.
after some tries I lost TWRP recovery access. I did with adb
> fastboot flash recovery twrp.img
> fastboot boot twrp.img
" that comes with this rom and now boots fine. still no camera.
Now my rear camera stopped working. in recovery tests its not working. I dont know if its an hardware or sofbrick because the phone fall in the ground while doing this these steps.
I even disassembly to if camera is well connected.
So im considering reflash with the stable version for HM2014813 wt86... with fastboot but but im avoiding that for not reconfigure and loose some data.
So i not recommend install super su TWRP in this version..