Lemon substitute?

My husband is allergic to citrus — not badly so, not to the level of “get him to a hospital” or “break out an epi pen,” but he should try to avoid it when possible.

. . . there are a lot of recipes that call for small amounts of lemon juice.

Is there anything that would make a good substitute for this? Something mildly acidic, I presume — maybe some kind of vinegar? White wine strikes me as the most “neutral,” but then again, I know little enough about this that I may have just typed utter nonsense. Recommendations appreciated.

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