I'm using 19.3 Cinnamon myself. If I remember correctly, I had to install a few dependencies first.
Try this first
sudo apt install python3.7 python3-pip python3-distutils python3-setuptools python3-wheel
then
git clone
cd nanovna-saver
python3.7 -m pip install .
Don't forget the space then . after install
then
python3.7 nanovna-saver.py
Should open after that. Let me know where you get errors.
Also I made a shortcut on my desktop to launch it.
Andrew Harmon