Xiaomi has started rolling out MIUI 12.5 software based on the Android 12 operating system for its four 2021 flagship smartphones.
Of course, we're still talking about the beta version of the software. Android 12 is being distributed as part of the Closed Beta program in China. The August 29, 2021 update (v21.8.29) is available for Redmi K40 Pro and Redmi K40 Pro+ models powered by Snapdragon 888 processor.
Xiaomi Mi 11 Pro and Mi 11 Ultra also got Android 12 with MIUI 12.5 Closed Beta shell, but with the August 31, 2021 version (v21.8.31). These flagships too are powered by Snapdragon 888 processor.
The update was previously available for the Xiaomi Mi 11. What's new besides Android 12 brought by the MIUI 12.5 test build is not specified. A stable release is expected at the end of the year.
Source: Telegram (1, 2)