Xiaomi has a good record for updating its smartphones, but that record does not stretch to the Mi Mix 3. Unfortunately, it seems that the device has been bypassed for an Android 11 upgrade too, despite being released on Android 9.0 Pie.
https://www.notebookcheck.net/The-Mi-Mix-3-may-have-been-overlooked-by-Xiaomi-for-Android-11-after-one-OS-upgrade.527236.0.html
Forget miui and get the pixel experience rom, currently android 11 is in beta and 10 has been my daily driver for 6 months or more. Has completely changed my experience with the phone, so many little quality of life features above and beyond what was in the miui rom.
Pixel=Google overload (as is the global MIUI ROM these days-Google spyware) Also not necessarily faster either or more efficient