Not canon? It was made by the og team.
The og said it doesn't matter if it's canon or not ......
Canon
"Early on, when we first thought
The Last Ronin would be clearly set in the original Mirage
TMNT canon, Kevin Eastman and I saw definite potential for more content for the story we were telling. But as time passed, and as we began to realize that
The Last Ronin was going to be set in its own multi-versal timeline (which we now lovingly call the Roninverse), ideas for prequels (including a new origin story) began to pop in our heads. Our first priority, however, was to get
The Last Ronin done the way we wanted it to be done. That first story had to be right before we moved on to other tales in this new
TMNT reality. When it was done, and the critical reception and sales were as fantastic as they ended up being, Kevin and I turned our sights to what we wanted to do next."
Not Canon