Changing the operating system (OS) on your Huawei Nova 9 involves replacing the default HarmonyOS (or EMUI, depending on the region) with another OS, typically a custom Android ROM or another operating system like LineageOS, AOSP, or similar alternatives. However, doing so requires a deep understanding of the process, as it can void your warranty, cause data loss, and even "brick" your device if not done properly.

Huawei devices have locked bootloaders and no official support for custom ROMs, and you also face the challenge of limited access to Google services due to ongoing restrictions. But it’s still possible to change the OS, provided you understand the risks involved.