Unlike the previous versions of Android OS in which only Google Pixel/Nexus devices were allowed to participate in the beta testing programme, the Android 9 Pie Beta program was open for many non-Google devices among which was Xiaomi Mi Mix 2. At that time, the Xiaomi had MIUI 9 on top of Pie however it has been replaced by MIUI 10 (still in Beta). Ever since the news broke out that Android Pie has officially arrived, Xiaomi has been busy stepping up its game by bumping up its OS version to MIUI 10. Xiaomi has already opened up the invitations to the Beta program and is targeting the global users of Xi Mix 2S. If you are interested, you can submit your application by August 9th and if you are selected, you will receive an official confirmation message on August 12th.
Apart from owning a Xiaomi Mi Mix 2S, there are other requirements that include downloading and installing QQ app for communicating, having a good grasp of English language, an unlocked bootloader, latest MIUI global Beta ROM on Mi Mix 2S, and more. Source: Xiaomi
