Specify a specific default kernel to use when running "jupyter-notebook" from the command line?

What is the correct way to specify a default kernel for Jupyter notebook to use from the command line?

I have quite a number of different projects with different Conda environments going on at the same time. Jupyter notebook does not recognize which environment I work in, so I need to always change the kernel from within the notebook, but it would be more convenient when I could already pass the correct default kernel when starting.

I have tried using --GatewayKernelManager.default_kernel_name="envname" and --MappingKernelManager.default_kernel_name="envname" but that did not work.

Even more importantly, is there a way to specify the kernel from the command line for jupyter nbconvert --execute ...? That would be very important in some cases.