The last time I looked into HarmonyOS, it was an intentionally vague umbrella name for a family of operating systems and kernels. On phones and tablets, HarmonyOS was a fork of Android 10 (this was when 13 was new). On embedded devices, it was a Linux kernel fork. There were supposedly some unifying features and APIs between them, but the documentation felt very much like Huawei didn’t actually want you to know what HarmonyOS is.