Drawing A Mesh Without A Camera

I have a number of camera that render 1 or few meshes, and I found out there's some drastic overhead about having a "camera", including some GUI calls. The overhead of a camera isn't needed.

For example, we render a hull to perform depth occlusion.

I found this; https://answers.unity.com/questions/1067005/how-to-render-without-camera.html

However, something is messed up with the matrices in it and it renders the mesh wrong. (Up is down, wrong rotation)

Someone know a guide on how to render without a camera?