@R0B0T0 The black cable has to be inserted directly into the Wii U, otherwise it can't be addressed by nintendont and it crashes.
Regarding the HDD it should be possible to make it boot even if it is inserted into a Hub as the Wii U OS handles the mounting to the disc drive of the wii and nintendont grabs the gc iso from the virtually mounted wii disc.
Maybe it crashes because of too much power draw from one port and you still need to split it up.
And I accidently linked the wrong issue, the one I meant was this one:
https://github.com/FIX94/Nintendont/issues/252
Some kind of reaction to my post would have been appreciated.
What is this entertainment unit you speak of?
Is your Wii U lacking some ports or do you have other devices connected there?
Maybe you really need to connect the hdd y data cable directly as well and power the hdd y power cable and the wii u gc adapter via a hub that is connected to a usb charger, that way it should work with only two free ports on the Wii U.
Edit: For me it also crashes with the hdd in the hub, carnage702 on github meant any peripheral accessed by nintendont then, so you need to change your setup a bit I guess.