I know the French version (and possibly others) have Sheik saying that she's a guy, but Sheik is just a disguise Zelda wears to hide from Ganondorf. And seeing as Zelda is female, Sheik is too. I don't get where people are coming from when they say Sheik is male.
Since she could change her complete appearance, darkened her skin, got red eyes, why couldn’t she change her gender as well ?
The things that make a lot of French Zelda fans (and possibly other fans from other countries, since Sheik must be described as a guy in other versions as well, as you said) think that Sheik is a guy are that he speaks using masculine nouns and pronouns, and that his appearance looks somewhat virile in OOT.
So you know, when you’re only 4 years old and see this character with those elements combined, it’s perfectly understandable that your first reaction is to think of him as a boy ê.e