RetroLab is an alternative JupyterLab distribution, built from the ground-up with JupyterLab components, giving the same look and feel as the Classic Jupyter Notebook interface.
See Also: For more information about RetroLab, see the RetroLab documentation and the RetroLab announcement blog post.
RetroLab is focused on a single document experience, but re-uses components from the more flexible (but complex) JupyterLab interface. This allows extensions to work between both interfaces, and streamlines the user experience so that they complement one another.
You can do anything with a Jupyter Notebook that you could do with JupyterLab. For example, see the intro.ipynb Jupyter Notebook, which is an introduction to this repository's content and contains some pointers to get you started.
Note: This interface is provided by the JupyterLite project, which embeds an entire JupyterLab interface, with many popular packages for scientific computing, in your browser. There may be some minor differences in behavior between JupyterLite and the JupyterLab you install locally.