I believe MIUI V12.0.5.0 introduces new issues as I found when I installed /e/ on my Xiaomi Note 9
I wrote to Xiaomi on a public forum that I intended to return my device as I had evidence that V12.0.0.5 changed the behaviour of the device so significantly that it was “not as adverised”. This post appeared soon after on Telegram.
https://xiaomidna.com/featured/how-to-downgrade-from-miui-12-5-to-miui-11/
In the preamble the author tells us “we are receiving so many comments and mail on our inbox that how we can go back to MIUI 11 from MIUI 12.5 or how to revert back to MIUI 11 from MIUI 12.5 without bricking our device.”
You decide if it offers a solution, but it demonstrates the issue for someone coming across it for the first time.
The author starts his tutorial with:
"It’s highly recommended to carefully read through the whole guide before doing anything with your device.
He finishes with
“What If You Can’t Downgrade MIUI Version”
The smartphone which is released after the 2nd half of 2017 might be affected by the ARB ban. This means if you have MIUI 12.5 Android 10, then you can’t downgrade from MIUI 12.5 to 11.
Anti-Rollback Protection
Xiaomi implemented anti-rollback protection in the latest versions of MIUI. Google’s anti-rollback security is a feature of Android Verify Boot 2.0. It prevents the device from booting."
XDA Developers offer another perspective
https://www.xda-developers.com/xiaomi-anti-rollback-protection-brick-phone/
