The UV is not specifically the texture that is applied, but how the texture is applied.
The UV for the mesh is when all the geometry has been laid out flat in the UV space of 0,1.
This video tutorial covers the basics of UVs and mapping them: The Basics of UV Mapping - YouTube
If you’re using a boolean to cut out parts of your geometry and you’ve not setup a proper UV this would explain the degenerate tangents.
Let me know if you have any other questions. I don’t mind helping where I can. 