[Python] Multiple Matplotlib versions make Spyder 6 unable to start the IPython kernel on...

I currently meet this error when starting Spyder 6.0.1 (installed with pip because the one available in apt package is stuck at version 4.2.1) on Ubuntu 22.04:

An error occurred while starting the kernel

/home/username/.local/lib/python3.10/site‑packages/matplotlib/projections/__init__.py:63:
UserWarning: Unable to import Axes3D. This may be due to multiple versions of Matplotlib
being installed (e.g. as a system package and as a pip package).
As a result, the 3D projection is not available.
warnings.warn("Unable to import Axes3D. This may be due to multiple versions of "


This is due to the fact that both the apt package python3-matplotlib (3.5.1) (needed as dependency for some other installed software) and the pip package matplotlib (3.9.2) (needed by myself) are installed, the first being available at: /usr/lib/python3/dist-packages and the second one at: /home/username/.local/lib/python3.10/site-packages/.

The Python path being the following:

>>> import sys
>>> for i,j in enumerate(sys.path):
... print(f"{i}: {j}")
...
0:
1: /usr/lib/python310.zip
2: /usr/lib/python3.10
3: /usr/lib/python3.10/lib-dynload
4: /home/username/.local/lib/python3.10/site-packages
5: /usr/local/lib/python3.10/dist-packages
6: /usr/lib/python3/dist-packages


Is there a way to explicitly set a different priority when loading a specific package in Spyder so that I can force Spyder to work with the Matplotlib library installed by apt in: /usr/lib/python3/dist-packages?

I don't understand either, because the Matplotlib message state is "warning", so it shouldn't block Spyder's startup.

Also, in Spyder there is the menu Tools > PYTHONPATH manager which first seems promising but it's only to "append" new paths to the existing Python path as it says:

The paths listed below will be passed to the IPython console and to the Editor as additional locations to search for Python modules."
​

and it's currently empty.

Last but not least, when starting an IPython console, I can load matplotlib 3.9.2 without any troubles, so why can't Spyder?:

$ ipython3
Python 3.10.12 (main, Sep 11 2024, 15:47:36) [GCC 11.4.0]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.28.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import matplotlib as mpl

In [2]: mpl.__version__
Out[2]: '3.9.2'



The very last option would be to permanently uninstall the Matplotlib 3.9.2 pip package but if I can avoid that, I would be glad.

Spyder version:

* Spyder version: 6.0.1 (pip)
* Python version: 3.10.12 64-bit
* Qt version: 5.15.2
* PyQt5 version: 5.15.7
* Operating System: Linux-6.8.0-47-generic-x86_64-with-glibc2.35

Continue reading...