You can add the community tag to the post arguments and you don't have to worry about paying for the pro version. Of course the community edition doesn't have all the full features as the pro version. Check this site for a comparison: https://www.ntop.org/products/traffic-analysis/ntop/
How do I retain my setting upon restart or reboot. When I restart the docker all my ntopng preferences and settings revert back to their default settings.