Flash R7800-factory-to-ddwrt.img build from Netgear firmware.
Once dd-wrt is running you have to use ddwrt-netgear-R7800.bin
to flash future updates.
Latest BIN available here: http://www.desipro.de/ddwrt/K3-AC-IPQ806X/
Currently known issue:
-2G and 5G leds are not operational since they cannot be controlled through gpio.
Current opensource wireless driver has no support to control these leds.
If you want to revert to netgear firmware flash: ddwrt-to-netgear-fw-R7800.bin