Headless rendering opacity issue with depth peeling

Locally, I found that opacity is not rendered properly unless you set `s.scene.renderer.use_depth_peeling = True` as per this issue: https://github.com/enthought/mayavi/issues/574

I am now running on a headless server using `Xvfb` as per https://docs.enthought.com/mayavi/mayavi/tips.html#rendering-using-the-virtual-framebuffer but when I set `use_depth_peeling = True` any surfaces with opacity completely fail to render.

Without depth peeling the render works, but doesn't look good -- I have seen in a number of places that this is a known issue with vtk.

I believe the exact same issue is happening here: https://github.com/pyvista/pyvista/issues/2592

Are there any other alternatives to `Xvfb` for headless rendering I could try out?