At the Chaos Communication Congress failoverflow showed us a Linux running on the PS4 with a special version of pokemon running on it. They didn’t talk about it like the 3DS hacking just a few slides and a video of it in action. 
Now it’s hard to say what firmware they are using to do this with but if I had to guess I would say 1.76Fw as we know it has the WebKit exploit in it but they use the PS4 user guide as their entry point. Thanks to biteyourconsole they recorded this for everyone to see, you can check out the short video below.