Edit the contents of the file as in the following article.
Build dtb with the following command and
make ARCH=arm64 O=$TEGRA_KERNEL_OUT dtbs
I proceeded to flash dtb with the followng command:
sudo ./flash.sh -r -k DTB jetson-nano-devkit-emmc mmcblk0p1
Looking at dmesg, it seems that the sd card is still not found.
Where did I make a mistake?