jupyter client menu [File] > [Open] fails with "404: Not found" at localhost:8888/files/undefined/tree

Sorry if I am not reporting in the right place, but I am running out of ideas after a whole day trying to troubleshoot the issue. Everytime I launch a notebook (or just a notebook client) from any environment where python >= 3.10.0.0, < 3.11.0, I get this:

> jupyter nbclassic my_notebook.ipynb
[I 2022-10-28 17:34:09.727 ServerApp] jupyterlab | extension was successfully linked.
[I 20221028-173409.736 ServerApp] nbclassic | extension was successfully linked.
[I 2022-10-28 17:34:09.752 LabApp] JupyterLab extension loaded from /usr/lib/python3.10/site-packages/jupyterlab
[I 2022-10-28 17:34:09.752 LabApp] JupyterLab application directory is /usr/share/jupyter/lab
[I 20221028-173409.755 ServerApp] jupyterlab | extension was successfully loaded.
[I 20221028-173409.759 ServerApp] nbclassic | extension was successfully loaded.
[I 20221028-173409.761 ServerApp] Serving notebooks from local directory: /home/USER/Scratchbooks/Data-science
[I 20221028-173409.761 ServerApp] Jupyter Server 1.21.0 is running at:
[I 20221028-173409.761 ServerApp] http://localhost:8888/tree
[I 20221028-173409.761 ServerApp]  or http://127.0.0.1:8888/tree
[I 20221028-173409.761 ServerApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[I 20221028-173412.362 NotebookApp] 302 GET /notebooks/my_notebook.ipynb (127.0.0.1) 1.24ms
[I 20221028-173413.418 ServerApp] 302 POST /login?next=%2Fnotebooks%2Fmy_notebook.ipynb (127.0.0.1) 1.26ms
[W 20221028-173414.606 ServerApp] 404 GET /nbextensions/widgets/notebook/js/extension.js?v=20221028173409 (127.0.0.1) 10.55ms referer=http://localhost:8888/notebooks/my_notebook.ipynb
[I 20221028-173414.893 ServerApp] Kernel started: b6f2f5d6-...............5295222a4ce

In addition when I go to the nb's [File] > [Edit] > [Open] menu item to get a directory listing where the nb is, a new window tries to open in Firefox at http://localhost:8888/files/undefined/tree and fails with: 404: Not found. You are requesting a page that does not exist. Simultaneously I get this log entry:

[W 20221028-173418.416 ServerApp] 404 GET /files/undefined/tree (127.0.0.1) 1.28ms referer=http://localhost:8888/notebooks/my_notebook.ipynb

My only extensions are:

> jupyter nbextension list
Known nbextensions:
  config dir: /home/USER/.jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled 
      - Validating: OK
      nbextensions_configurator/config_menu/main disabled
    tree section
      nbextensions_configurator/tree_tab/main disabled
  config dir: /home/USER/.pyenv/versions/3.10.0/etc/jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled 
      - Validating: OK
  config dir: /usr/local/etc/jupyter/nbconfig
    notebook section
      nbextensions_configurator/config_menu/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/config_menu/main
    tree section
      nbextensions_configurator/tree_tab/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/tree_tab/main
  config dir: /etc/jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled 
      - Validating: OK

Note: When I launch a nb from any Python env whose version is before than 3.10.0, there is no issue. I have rebuilt all my virtual envs and custom iPython kernels (those I use are between Python 3.7.0 and 3.10.7) and did cross trials to sort of cover the range of possible combinations of nb iPYthon kernels and launch environment Python versions... The only discriminating variable in those trials seems to be not the iPython kernel used by the nb but only the Python version in force in the environment where he nb is launched.
How can that be ? I'm stumped.

ipython-contrib / jupyter_contrib_nbextensions

jupyter client menu [File] > [Open] fails with "404: Not found" at localhost:8888/files/undefined/tree #1610