The traceback mentions Python 3.9, e.g.
File "D:\msys64\mingw64\lib\python3.9\site-packages\pip\_vendor\pep517\in_process\_in_process.py", line 351, in <module>
On Windows it’s recommended to use the Python Launcher py:
py -3.11 -m pip install matplotlib
I have it installed here on Python 3.11 on Windows without a problem.