The Netgear readynas is essentially a x86 computer, with a handy Serial TTL interface at the back.
However, it’s not entirely straight forward. Unetbootin-created usb-media did not boot, but the debian netboot iso appears to boot. However, it doesn’t support serial console out of the box.
After remastering the netboot image with settings for console, I was ready to try again – holding the ‘backup’ button on front while powering up. And presto – a debian boot menu appeared. From thereon it was pretty straight forward. If you want, you can grab the image here – debian-8.2-serial.iso. It can we written to CD with your favourite recording software, or written to a usb stick with dd. For the Netgear, use a usb stick.
The performance went from 450Mbps to 950Mbps, so clearly the way outdated software that Netgear shipped it with was inadequate for the hardware.
So now I have a Debian computer, which can do anyting – not limited to what Netgear wanted me to do. And as a bonus it even performs better!