Xiaomi Mi Mix 2S was one of the few devices that got the beta version of Android Pie alongside the Google Pixel devices. After the official release of Android 9, Xiaomi started closed alpha testing of the Android Pie builds. They were testing the system in China, and @xiaomiui Telegram channel was able to leak some photos along with the actual build. Being an alpha version, of course, it was unstable and full of bugs.
Now, thanks to a tip from @Tadi777 on our Telegram group, we have the link to the latest beta version of Android Pie for Xiaomi Mi Mix 2S. There are two versions available, one for the Global ROM and another for the Chinese ROM. Keep in mind that both of them are MIUI Recovery ROMs. So, you don’t really have to wipe anything from the device before installing. You can flash them via a custom recovery like TWRP.
Looking at the build.prop of the builds showed that both of them come with the latest September security patch. Usually, beta builds from Xiaomi are quite stable, and in most cases, suitable for daily use. You may encounter some weird bugs every now and then, but they’re much more optimized than the alpha builds.
Android 9 Pie brings a lot of new features to the table. Many of them are aesthetic, like refreshed Material Theme, while some of them focus on security and overall behavior of the system. Availability of the latest and greatest Android is currently limited to the handful of devices, including the Pixel line of devices and Essential PH-1. Apparently, Xiaomi and Huawei want to be one of the first ones to put out Android 9 Pie for their devices. Links for the Global and China versions of the Xiaomi Mi Mix 2S are available below.