locally you need to use the public host and port.

n/a

Oh I thought runinng railway run python [manage.py](manage.py) createsuperuser uses the public host and port. So what you're saying is that I need to get the public url from the railway postgres then update my .env file to get it working?

nope, it uses whatever variables you have set on the linked service, you would need to overwrite that locally, a local env file should be sufficient