How to render skybox to all the cameras?

Yes, more like this, thanks for correction.

apply only the rotation and scale elements of the model-matrix

Are they available as shader inputs? The manual only has the Model matrix. So either I need to decompose it, or set shader inputs, right?

About your advice about working directly in clip-space - I am afraid I know less than you here, so I’ll skip this for now.

With this said, I must say am kind of new to shaders. I learned some HLSL to write a basic DirectX11 renderer, but it is not applicable in Panda.

I’ll try to do what you suggested and post here if it works.