sudo pacman -S jupyter-notebook
sudo pacman -S kde-applications
jupyter-notebook
As idiotic as it is, jupyter tried to start wine, after the update of the whole kde, it started ... Konqueror. Yup. Life's complicated when you update a linux system. Luckily, it can be solved also with
jupyter-notebook --browser=firefox
but I found it too late. So anyway, now I have konqueror.