Xiaomi sub-brand Redmi has released the stable ROM of Android Pie for the Redmi S2 in China and the Redmi Y2 (rebranded S2) in India.
The new firmware requires a download of 1.4GB and sports version number MIUI V10.3.3. It lets you lock Google Contacts and comes with a fix for an issue related to deletion of contacts from the SIM card. You can check out the full changelog below:
The update is rolling out over the air and it should be a few weeks before it reaches all the units.
Xiaomi Android Firmware Updates