Where did you get this Xavier NX? Is it Nvidia devkit or from partner?
If that’s our devkit, you should be able to reflash your device via JetPack by SDK manager, not matter the NX module is SD card or eMMC verion.
You can download the SDK Manager on your Ubuntu host PC. (for JetPack 5.x, plese use Ubuntu 20.04 as host OS, other JetPacks should be 18.04 version)
Follow the guidance. Put your board into recovery mode and flash it.
See also: SDK Manager unable to find Jetson AGX Orin Development Kit