@dobey and that is exactly the problem I am facing and why I am seeking help here: it does not work. the pin which is set to unlock the phone does not work for authentication.

I am using the FP2 and am stuck with the terminal: Starting the application, it asks for authentication and neither phablet, ubuntu or the pincode/passphrase works as root password. Can't even type in terminal because the authentication screen is on top and without getting through it won't let me access terminal. How can I fix this?