From comment on this and other sites it seems like the kicad-cli pcb render command should be able to include the 3D models into the 2D output.
However I only get the bare board rendered and none of the CLI documentation or help is indicating how to enable the inclusion of component models. The board renders perfectly in the 3D viewer including components. Is this expected?
KiCad 9.0.1 on Ubuntu (WSL).
Edit:
After apt update & upgrade I now have at least the standard KiCad models in the output. The models from my own library are still missing but are perfectly visible in 3D Viewer.
Where ${KICAD_DOCUMENTS_HOME} is pointing to the parent directory of my library, containing the symbols, footprints and 3dmodels directories, so:
${KICAD_DOCUMENTS_HOME}/symbols
${KICAD_DOCUMENTS_HOME/footprints
${KICAD_DOCUMENTS_HOME/3dmodels