Resource:
ROS2 Foxy + Ubuntu 20.04 Install on a Jetson Nano
Step 1: Download 7Zip in order to be able to unzip .tar file types
Step 2: Download Balena Etcher to be able to flash the microSD
balenaEtcher - Flash OS images to SD cards & USB drives
Step 3: Download the image
Xubuntu 20.04 Focal Fossa L4T R32.3.1 - Custom Image for the Jetson Nano
Step 4: Unzip the downloaded file. You will need to unzip the downloaded file and then unzip the result again in order to get the image file you need.
Step 5: Plug in your MicroSD and flash it using the Balena Etcher software with the image that you obtained from step 4
Step 6: Eject the MicroSD after that step 5 has been completed and plug the microSD at the back of the jetson nano.
Step 7: Install ros2 Foxy on the jetson Nano