Starting from 10.8, the use of sage with system jupyterlab needs some work but it is possible. From my experience, one has to edit a proper kernel.json file and reinstall the kernel after any new building process of sage. I have no clue how to make it more direct.
I found another issue using some installed packages, e.g. fricas, which works in command line and does not work in a notebook. It seems to be a path problem; local/bin is in the path for command line but only venv/bin is in the path for jupyter. Is there any way to correct it?
Enrique.