Xiaomi launched the Mi 6 back in April 2017 originally with MIUI 8. Two years on, the Chinese manufacturer has released an Android 9 Pie beta build for its China and Global branches. Proceed with caution.
https://www.notebookcheck.net/There-s-life-in-the-old-dog-yet-Xiaomi-is-testing-Android-Pie-on-the-Mi-6.418978.0.html