We don't know any good Supy.io open-source alternatives yet.
You are more than welcome to suggest any alternatives that you know of, or ask the community for suggestions.
Alternatively, we recommend checking out LibHunt for open-source libraries and alternatives to Supy.io.
Supy.io is operating in a very underserved market - most existing solutions are old, clunky and very expensive. Predictive inventory management has huge potential to transform F&B businesses, given their generally low margins.