SickChill ReadyNAS app are available from the ReadyNAS App Store or Latest Release.
Early releases will be available from the GitHub Releases.
You must have python 3.6 or later to use this package!
An example script that might work for you directly is available here: https://github.com/SickChill/readynas-sickchill/blob/master/build_python.sh
The script must be run as root or you can input the commands one by one as root.
sudo apt-get install devscripts build-essential lintian
debuild -i -us -uc -b