A user found a way to rollback to Android Oreo from Android Pie for Mi Box S users.
Many users like me are searching for a way to rollback to Oreo until a stable release of pie is not released. So finally now we can rollback.
It requires a pc though.
I have serious doubts as to this possibility.
There does not exist an Oreo .img file that can be flashed to MDZ-22-AB, nor is there a userdebug rom.
When the referenced technique was developed to downgrade Nougat to MM, there were plenty of viable rom sources.
With userdebug rom versions many kinds of hacks, tricks and capturing and writing partitions were available.
Not these days....