you should just need to add the force argument on the sysupgrade method. Obviously be sure you do not keep settings across the upgrade. Make sure that the image hash/checksum matches before you run the command with the force argument.
sysupgrade -F -n -v /tmp/openwrt-22.03.2-ath79-generic-zyxel_nbg6616-squashfs-sysupgrade.bin