So we noticed immediately after upgrading to 4.24 from 4.23.1 that the Paper2D Normal Buffer was acting as if it was Y-Up… Thus things like ambient occlusion and any other world normal based system was horrifically broken on paper2D Sprites and flipbooks. This seems to be from a recent optimization that utilizes a new vertex buffer. At the end of the buffer you can just simply change TangentZ to GetTangentY()
Engine/Plugins/2D/Paper2D/Source/Paper2D/Private/PaperSpriteVertexBuffer.cpp line 150
Old
TangentBufferData[2 * i + 1] = Vertices*.TangentZ;
Fix
TangentBufferData[2 * i + 1] = Vertices*.GetTangentY();
I am not a graphics programmer… so its possible this could be wrong in other ways, but at the moment this seems to have fixed the issue for us.