For "middle ground" projects like this (criteria: a common enough problem that lots of people _should_ have thought about it -- but it may not be a lucrative co

For "middle ground" projects like this (criteria: a common enough problem that lots of people _should_ have thought about it -- but it may not be a lucrative core business area -- and there aren't any household-name open source projects that cover it), I often turn to GitHub repository search to see what's available. Based on that, your best bet might be https://github.com/ReceiptManager/receipt-parser-legacy https://github.com/ReceiptManager/receipt-parser-legacy, which is a Python library built on top of the Tesseract OCR engine. You can use it containerized, in Android/iOS applications, or via your own Python scripts.