it's 8 hours i am trying to fix this.
The mesh is perfectly smoothed (edges)
if i import the Xnormal-baked map in Marmoset, it works completely fine (first image. it get seams on 3DS MAX tangent space. if i obviouslt invert Y, it works).
If i import the same thing in Substance Painter, the seams appear and he bakes them if i export his textures inside Marmoset. And in that case even if i try to invert Y, the seams are still there.
I tried OpenGL and DirectX, but zero effect. It always sees and bakes seams. Can't find a way.
I give up, I am really getting a mental burnout.