Export PMX as OBJ

1. Import MMD model from Scene Setup
2. Select the mesh and click Convert to Blender in Model Setup
3. File > Export > Wavefront (.obj) then enable PBR Extensions, choose path mode you desire (I chose Copy to reset texture path)
4. if there’s any glitches in model visibility, you should disconnect Texture Alpha by opening Shader Editor

It worked in my Preview app.

credit: Sucrose (Genshin Impact)