This is based on Method 2 in https://websiteforstudents.com/installing-the-latest-python-3-7-on-ubuntu-16-04-18-04/
First, you need to install Python 3.7 (you will currently have Python 3.5.2):
sudo apt update
sudo apt install software-properties-common
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt update
sudo apt install python3.7
You now have two different versions of Python 3!
$ python3 --version
# Outputs 3.5.2
$ python3.7 --version
# Outputs 3.7
So you need to use pipenv but tell it to use Python 3.7 instead.
In a brand new folder do this:
pipenv --python=python3.7 install jupyterlab
Now you should be able to continue using the regular commands in that folder, e.g.
pipenv install altair
pipennv install pandas
pipenv run jupyter lab
Thank you so much @ZakiOro. It worked like a charm