One guide per aisle. Each is built around the mechanism rather than a brand list. “Soy sauce is brewed on wheat, and tamari is the exception” stays true forever and works on a bottle nobody has written about. A list of brand names goes stale the moment anyone reformulates.
This site answers the question you knew to ask. The app answers the one you didn't: the barley malt in a rice cereal, the wheat starch in a gummy. Scan the barcode, or photograph the panel when the barcode isn't in any database, and CiCi shows which words on the label produced the answer.
14 days free, then $29.99 a year. Cheaper than Fig, and it does what three separate apps do. This website stays free forever either way: every answer on it, permanently, with no account.