JupyterLab Server sits between JupyterLab and Jupyter Server, and
provides a set of REST API handlers and utilities that are used by
JupyterLab. It is a separate project in order to accommodate creating
JupyterLab-like applications from a more limited scope.

jupyterlab_server 2.16.3 is the last possible version for Slackware
15.0. Newer versions would require a newer python-requests.