Xiaomi Mi Mix 2S and Mi Mix 3 receive new stable MIUI 12 updates
MIUI 12 is rolling out to the global versions of the Mi Mix 2S and Mi Mix 3. Other editions of the two devices have already been upgraded to Xiaomi's latest OS, including the Russian version of the Mi Mix 2S. The Mi Mix 3 5G, on the other hand, is unlikely to receive MIUI 12 or even Android 10 any time soon. The 5G smartphone remains on MIUI 10 and Android 9.0 Pie, despite Xiaomi's incessant upgrade schedule for MIUI 11 and now MIUI 12.
The global version of the Mi Mix 2S is receiving V126.96.36.199.QDGMIXM, whereas Xiaomi has issued V188.8.131.52.QEEMIXM for the Mi Mix 3. Both updates are being rolled out as over-the-air (OTA) upgrades and should be available to download now. However, Xiaomi typically releases OS upgrades in batches, so your handset may not receive MIUI 12 for a while yet.
Nonetheless, you can try to download and install the update manually. To do so, download one of the recovery ROMs via the links below and place the downloaded file in your device's onboard storage. Then, head to Settings>About phone>System and look for three vertical dots at the top of the screen. If they are not there, tap the MIUI logo 7-8 times to enable them. Finally, click choose update package and navigate to the file that you downloaded. If your device can verify the recovery ROM, then it will reboot and flash the update. The process should take up to 10 minutes.