The September 2020 security update for Redmi K30 Ultra comes with the build number V12.0.12.0.QJNCNXM and cost 211MB to download the package. You should get a notification for the update or check it manually by heading to Settings -> About phone -> System update. You can also use the download update using the link given below, and manually install it. Redmi K30 Ultra – V12.0.12.0.QJNCNXM – Download Link
Xiaomi Redmi K30 Ultra update changelog:
System:
Update Google security patch (2020/09) to improve system security
Other optimizations
Optimize Wi-Fi connection Optimize hotspot connection Fix the problem that the low probability charging icon does not display Fix the problem of WLAN