The product entry on Spar’s Austrian website for Hafer-Flocken contains this information on allergies. (As translated by Google)
Contains: Cereals containing gluten and products made from them
I’m not 100% sure it’s the identical product as the English name given is oat meal rather than oat flakes.
This is a situation similar to what consumers with food allergies face - the critical substance is not in the food items per se, but cross-contamination may be a problem.
Oats are gluten-free1, but during processing and packaging, residue of e.g. wheat may get mixed in with the oat. While this is probably minimal and not a problem for consumers who avoid ...