An adaptation doesn't have the requirement of following an existing story. They are adapting parts of Tolkien's work to tell a story. Westside Story is an adaptation of Romeo and Juilet. I haven't objected to you saying it is not canon. As I said before you keep making things up in order to argue.
On the intro for the show amazon has "Based on 'The Lord of the Rings' and appendices by J.R.R. Tolkien". The trivia, under x-ray, also indicates "Most of the details and elaborations told herein are derived from 'The Lord of the Rings', its prologue entitled 'Concerning Hobbits', and its appendices, A through F, where the intrepid traveler may journey to discover even farther horizons".
Which clearly indicates it is an adaptation. They aren't telling canon but are adapting portions of his work into their own story.