As for RenderMan, Pixar itself provides plug-ins that work with some software. On the other hand, the documentation for command line based use has been decreasing over the years, making it difficult for third parties to provide support.

RenderMan is an excellent renderer, but for the above reason, we recommend to use the standard path tracer and will remove RenderMan integration from the standard functionality in the next version. It will continue to be made available as an independent plug-in, but ongoing support will not be provided in the future.