Android Oreo was officially unveiled in August and Pixel devices were first to test it, and later pushed to some other OEMs. Recently, Xiaomi has joined the list with MI 6’s Android 8.0 beta testing. Now, the company is even expanding it further to Mi Mix 2. Today, the company has officially announced the closed beta testing programme for Mi Mix 2 based on MIUI 9. It will provide the experience of Android Oreo but not stability. Unfortunately, the beta ROM is restricted to China-specific devices, but we can expect it to be spread further to other parts of the world.
Since it is a closed beta, there are chances to be it buggy and limited availability. It is always advisable to don’t install the beta ROM on your primary device. If you are still interested to join this programme, you can enroll for it by visiting MIUI Thread. All the instructions are given there with detailed information. Moreover, Android Oreo comes with some interesting features, but MIUI is highly optimised UI, so you might miss some stock ROM features.
Source: MIUI Forum