[OpenWrt Wiki] NETGEAR D7800
https://openwrt.org/toh/netgear/d7800D7800 has an easy-to-use TFTP flashing recovery mode in the bootloader, similar as some other Netgear routers e.g. WNDR3700. The following steps are from Netgear R7800 page which works with D7800. Prerequisites for TFTP flashing A TFTP client for your computer. There are both command-line tools and GUI versions available.