This script has two python modules as requirements, libevdev and inquirer. If you want to run the script with your systemwide python environment, you can try to find the relevant APT packages (often named python-MODULENAME) to install the modules on your system.
Alternatively you can create a python virtual environment (you can easily find howtos) and install the requirements in the virtual environment using the pip tool. This way, the requirements will be installed for this project only.
Also keep in mind to never use pip as sudo, it should not manage your systemwide python modules because it will conflict with your package manager.
I mostly use GIMP.
I am also enthusiast about the https://graphite.rs/ project which is working in browser (love it or hate it for that).
Krita is amazing for drawing but may be intimidating.
I like MyPaint that I use as a whiteboard. It is easy to use and convenient