Finding a reliable app for scanning books and merchandise can be challenging. However, I'd suggest giving the Smart Engines OCR Scanner a try. It's a free app you can download on iOS and Android devices. The app is quite efficient and can scan various printed materials, including books and product barcodes. If you're looking for more advanced features, they have a paid version you can upgrade to. You can check out their website, smartengines.com, to learn more about their app and other products.

From what’s been said the .kmy file was saved in 2018. KmyMoney has changed a lot since then. Would it be worth using an older version of KmyMoney (version 4xx) to see if it works?
When I’ve used Notepad to view a .kmy file I do also get Chinese like characters even though the file is OK, just compressed. Have you tried right clicking the file in Explorer and get Windows to extract the file? What version of Windows are you using?
With what has been done to the file already it could have become corrupted at any step. Can you possibly get a fresh copy of the file from the original source?
Good luck!