Download the Ext4 image.
Put it at the MicroSD:
sudo dd if=openwrt-25.12.2-rockchip-armv8-friendlyarm_nanopi-r6s-ext4-sysupgrade.img of=/dev/mmcblk0 bs=4M status=progress conv=fsyncDownload the Ext4 image.
Put it at the MicroSD:
sudo dd if=openwrt-25.12.2-rockchip-armv8-friendlyarm_nanopi-r6s-ext4-sysupgrade.img of=/dev/mmcblk0 bs=4M status=progress conv=fsync