@OP
Thanks for not making this a "I bricked because I didn't read warnings help me guys pleaaaase I beg you my best friends for gbatemp magic to unbrick!!!" type of thread, came here with low expectations.
My Wii U bricked on itself, playing Mario & Luigi Partners in Time VC legit. Turn on, blinking blue light, thats it - dead. Sent it to repair more than a month ago, they still didn't find out what the problem is. Bought another used Wii U without pad while you still can get those on 5.5.1 - too bad unlinking NNID from a dead console is a pain in the A.