The Stable update V12.5.5.0.RJCCNXM has been officially released for Redmi 9 / 9 Prime (codename is lancelot). Before updating, please make sure you have downloaded the exact ROM matching your Xiaomi phone/tablet. In Fastboot mode, you can check model code by typing fastboot getvar product in cmd/shell.
The firmware files posted here are all official Xiaomi ROM, xiaomiROM.com do not own and never modified those firmwares，you will always download the file from Xiaomi server.
You may interest in those contents: Redmi 9 / 9 Prime ROM Topics Xiaomi Devices Index
Download Redmi 9 (lancelot) China MIUI 12.5 V12.5.5.0.RJCCNXM Recovery ROM with Android 11.0. Firmware size is 3.1 GB.
Download Redmi 9 (lancelot) China MIUI 12.5 V12.5.5.0.RJCCNXM Fastboot ROM with Android 11.0. Firmware size is 4.2 GB.