Hi, I just unlocked my Mi6X and had the problem to make TWRP permanent. Solution was fairly simple
1. copy TWRP onto yr phone
2.do what is mentioned on the first page of the MIUI Rom releases
from PC via fastboot
Code:
fastboot flash recovery twrp.img
fastboot boot twrp.img
3. now install TWRP.img again from within twrp
Done
I used twrp 3.2.3
Good luck (
) helpfull even you don't understand what he is saying