I think you have an old kernelspec pointing to an environment that doesn’t exist anymore, in your user directory, which has higher priority than a given Python installation’s default. You can remove this with:
jupyter kernelspec remove python3
which should give you a confirmation like:
Kernel specs to remove:
python3 /Users/alexandre/Library/Jupyter/kernels/python3
Remove 1 kernel specs [y/N]
After this, if you run jupyter kernelspec list you should see an entry for python3 in your environment, like:
Available kernels:
python3 /Users/alexandre/anaconda3/share/jupyter/kernels/python3
If you don’t see that, you can recreate it with:
ipython kernel install --sys-prefix