Hi I just purchased a used r7800 from ebay with a stock firmware. I'm attempting to tftp flash the kernel from recovery mode from my linux laptop. After flashing the power light stops flashing white and goes black but the router never reboots. All else seems fine - my device is 192.168.1.2, router at 192.168.1.1, tftp on verbose trace binary shows all packets sent and received for the factory.img file (http://downloads.openwrt.org/releases/19.07.7/targets/ipq806x/generic/openwrt-19.07.7-ipq806x-generic-netgear_r7800-squashfs-factory.img).
It appears to be a working router - it boots normally into the normal netgear setup mode which I have not attempted to configure.
any helpful suggestions appreciated as to how to track this down.