Will note that the generated meshes here seem to give incorrect results with the corrected red channel which leads me to believe there is an issue with the tangents on these meshes. Could be a Godot issue because I do recall seeing this issue before in it.
That format parameter in the Normal node should not be used anymore. Just let it generate the "default" normals, which should render correctly in the preview. Correct normals are then generated when exporting for each engine.
And yes, the tangents on the preview are wrong (was an issue in Godot's default meshes when I started Material Maker, and fixed since then).
You can indeed trivially modify the normals format as needed using Decompose and Combine, but I'd recommend SwapChannels that is easier. And if you need new export options, please ask. :)
Thanks for the reply!
No, it is now fixed, but the first releases of Material Maker used a Godot release with the flipped tangents problem. All normal map conversion should now be done in the Material node, the format parameter of the Normal node should not be used anymore.