Today Xiaomi has started rolling out the update to Android 10, with MIUI 11 on top, for the Mi Mix 3 from 2018. We’re talking about a global stable version, no “beta stable” shenanigans here, and no Chinese-only stuff.
The update is currently being released for “other global regions,” i.e. non-India, Indonesia, Russia or the EU, as they have their own firmware codes. Even, it’s a beginning and hopefully we’ll see the update coming soon to all “world” regions (in Xiaomi’s parlance).
If you are fortunate enough to have the “other world” ROM on your Mix 3 then expect to see a message asking you to install MIUI 220.127.116.11 (QEEMIXM) on your computer. It’s a ~2 GB download, and once you get it up and running, you’ll also get the security patch level of February 2020, as well as a range of bug fixes and different performance optimisations.