I think this is a great writeup, and I find Irish myth fascinating, but I have seen a lot of people's takes on what connections to some mythos or work of fiction (e.g. Bersek) and just want people to keep this in mind:

Visual or thematic influences are not the same thing as reference sources.
Works of fiction are much more than the sum of their various sources of inspiration.
The Erdtree is not Yggdrasil.
The Erdtree is not The Great Spiral Tree.
It is the Erdtree.
It has it's own identity that is unique to Elden Ring's world.

Just as we should appreciate its sources of inspiration, we should appreciate the world of Elden Ring for what it is within the context of the game itself as well -- and as the collaborative work of Miyazaki and GRRM.