If this is a third party carrier board, then you’d have to check the support software from that manufacturer. For the NVIDIA dev kits, you’d want to use a matching release of L4T for what the SD card has. Mostly that means get the most recent L4T R32.x (L4T is Ubuntu plus NVIDIA drivers, and is what gets flashed), and use the JetPack/SDK Manager from that to flash the Nano. There is also a way to create SD cards from that in the tools directory if your current SD card is using an incorrect release. Note that JetPack/SDKM is a GUI front end for flashing, and L4T is what gets flashed. The two have their releases tied together. Use the instructions from the release you use; you can find that from here (just to emphasize, you want a recent R32.x L4T, which is a recent JetPack 4.x release):
On your host PC where you installed the JetPack/SDKM (you’d use an Ubuntu 18.04 host PC) you just start it via the icon, or via:
sdkmanager &
The command line content (and other content) on the host PC would be somewhere under:
~/nvidia/nvidia_sdk/JetPack...version.../Linux_for_Tegra/
Feel free to ask more questions.