This is for anyone who is looking for an up-to-date solution for launching and connecting to Jupyter kernel on remote systems via SSH.
During the summer of 2025, I spent a month implementing a python package that does exactly that. Kernels can be spawn directly from the JupyterLab UI or from the command line.
Python package: https://pypi.org/project/sshpyk/
Docs and GitHub: https://github.com/casangi/sshpyk/