Nook HD+ ?
I got my hands on a Nook HD+ cheap and was wondering if this method to install UT is still viable?
This device is not supported by UBports (https://devices.ubuntu-touch.io/) and the link you gave is from Canonical...
I'm no expert but many changes occured since that era and I cannot expect this procedure to work with the latest versions of Ubuntu Touch.
Wait a bit for a more insightful answer.