OpenWrt on Actiontec GT784WNV

Hola

I'm having trouble flashing OpenWRT onto the Actiontec router.

I tried the stock firmware web-based update (it rejects the OpenWRT bin file) and TFTP. which shows:

tftp -i 192.168.1.1 put install__openwrt-15.05.1-brcm63xx-generic-96328avng-16M-flash-generic-squashfs-cfe.bin
Transfer successful: 8388864 bytes in 13 second(s), 645297 bytes/s

But the stock firmware remains.

I'm posting this in case anybody else has this router and can write some proper documentation.

The wiki was not helpful.

https://openwrt.org/toh/actiontec/gt784wnv

What happens if you try 17.01.6 or 18.06.1 instead of the ancient 15.05.1?