Reporting according to [[https://openwrt.org/docs/guide-user/installation/ar71xx.to.ath79|https://openwrt.org/docs/guide-user/installation/ar71xx.to.ath79]]
because from what I gather, that is probably the cause for the upgrade failure.
Model NETGEAR WNDR4300 Architecture Atheros AR9344 rev 2 Firmware Version OpenWrt 19.07.3 r11063-85e04e9f46 / LuCI openwrt-19.07 branch git-21.357.58233-6f349c9
sysupgrade -n openwrt-21.02.1-ath79-nand-netgear_wndr4300-squashfs-sysupgrade.bin
fails with
Device wndr4300 not supported by this image
Supported devices: netgear,wndr4300
Invalid sysupgrade file.
Image check failed.
Image downloaded from
https://downloads.openwrt.org/releases/21.02.1/targets/ath79/nand/openwrt-21.02.1-ath79-nand-netgear_wndr4300-squashfs-sysupgrade.bin
Checked https://openwrt.org/docs/techref/targets/ar71xx-ath79
Also tried the SNAPSHOT from https://downloads.openwrt.org/snapshots/targets/ath79/nand/openwrt-ath79-nand-netgear_wndr4300-squashfs-sysupgrade.bin
sysupgrade -T openwrt-ath79-nand-netgear_wndr4300-squashfs-sysupgrade.bin
Device wndr4300 not supported by this image
Supported devices: netgear,wndr4300
Invalid sysupgrade file.
Image check failed.
dmesg output attached.
And last, but not least, thanks for this excellent project. /Yan