There have been some devs talking the past few weeks, making some progress. Ricky, the dev making amlogic customization toolkit, and is wanting to include us in his next update, BUT he does not have a mi box to do what he needs.
Send him your bricked box, he does some tinkering, and hopefully we come out with a open system for developers to play with! He sends back after. Success!
This thread started for the AA model, but switched to AB quickly.
This is what he already created for amlogic devices! Right now still no downgrades without losing drm.
https://www.google.com/amp/s/forum.xda-developers.com/android-stick--console-computers/amlogic/opensource-amlogic-tools-t3786991/amp/