This is an iteration of the MIX 4 MIUI 12 ROMs. The first MIUI 12 firmware or update for MIX 4 has already been released on 2021-08-26 by Xiaomi. You can now download the stable, weekly, or beta MIUI 12 ROM for your phone/tablet with device code odin. The last version of MIX 4 MIUI 12 ROM has been rolled out on 2021-10-21. It is recommended to update to the latest MIUI12 to experience the new features. If you want to upgrade or downgrade your MIUI version, you can find more details on the MIX 4 ROM section page.