Jupyter notebook does not detect Python kernel when run

Python files run just fine, but Python code in Jupyter notebooks does not run.

Error:
`Running cells with 'Python 3.10.6 64-bit' requires ipykernel package.
Run the following command to install 'ipykernel' into the Python environment.
Command: '/bin/python -m pip install ipykernel -U --user --force-reinstall'`

Both Python and Jupyter extensions are installed.

According to the VSCode documentation, these extensions should allow Jupyter notebooks to run on any installed Python kernel:
"Without the Python Extension installed the Jupyter Extension can pick up kernels installed into Jupyter registered locations and run them. But with the Python Extension installed new options are opened up for Python notebooks. Instead of being restricted to just registered Jupyter kernels any Python environment, meaning a Python interpreter and an associated location for Python packages, installed on the system can be used as a kernel to execute Python code in. The default kernel for Python is provided by the [IPyKernel package](https://ipython.org/). If you select an environment on the system that does not have IPyKernel installed and attempt to run the notebook you will be prompted to install IPyKernel. If it's installed, that environment can be used as a valid kernel for Jupyter notebooks in Visual Studio Code." (https://github.com/microsoft/vscode-jupyter/wiki/Jupyter-Kernels-and-the-Jupyter-Extension#python-extension-and-ipykernel)

Reproduce the failure by running a notebook in the Flatpak VS Code environment with the reported Python 3.10.6 kernel, then inspect how the Python and Jupyter extensions discover and validate kernels. Done means the installed environment can run notebook cells without the ipykernel error, with a regression check for this setup.

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