Did you format data prior reboot?
Regards
Sent from my Mi 11 Ultra.
Dang this was the problem.
So.
(if you are in a messy situation)
1) Reset to stock via MiFlash and the original image
2) Just go on with setup, ignore/skip all
3) Have to shutdown -> fastboot, then use MiUnlock if you opted for clean_and_lock option in MiFlash.
4) Once unlocked and ready, boot and then shutdown -> fastboot once again
5) Boot the twrp image (twrp-3.6.2_12-v5.6_A12-star-skkk.img)
6) Copy up the Xiaomi EU file now via mtp, or you can copy it when you boot the phone normally
7) Install it, wait for it to finish
8) DO NOT REBOOT, go into wipe and pick Wipe Data.
9) Now it'll boot.
Note: If you used the fastboot install for Xiaomi EU, you can't switch, you need to do these steps. Because I had that, and there I just got like 3 big errors and I could not boot.