Is there a way to override the default port for the jupyter notebooks that get launched by CLI?
Yes it is possible, thanks to a community PR that Nehil Jain contributed last year.
If you wish to override the default jupyter notebook command then you can set GE_JUPYTER_CMD environment variable. This is especially useful for running Great Expectations inside dockerized environments. For example:
export GE_JUPYTER_CMD='jupyter notebook --port=80'
This StackOverflow post talks more about the options that you can pass to jupyter: