Jupyter notebook don't start (ubuntu)

This post says for using pip3 to use the following to run the notebooks:

python3 -m notebook

You clearly have jupyter something installed.
Maybe try some of the other suggestions on that page I reference if that particular one doesn’t help? Then dig in to what you see from the following if you need more help:

jupyter –paths

If all that fails, or if you’d rather do it maybe a better way that would allow more reproducibility for your efforts in the long run, I’d suggest installing conda (or mamba) and learn to run things in conda envs.