Learn Portuguese (Portugal): O apicultor não deu o pólen a ninguém, tirando tu. - Except for you, the beekeeper did not give the pollen to anyone.

Usually, prepositions are followed by prepositional pronouns like ti or mim (for example, para ti or sem mim). However, prepositions of exception like tirando, exceto, and salvo break this rule. They must be followed by subject pronouns. That is why we use tu here, and would use eu instead of mim (for example, tirando eu).

Is tirando exactly the same as exceto in this context?

Yes, they are completely interchangeable. Tirando literally means taking away (it is the gerund of the verb tirar), but it is widely used as a preposition meaning except for or apart from. It often sounds a bit more conversational and natural in everyday spoken Portuguese than exceto or salvo, though all of them require a subject pronoun like tu.

Why do we use both não and ninguém? Doesn't that make a double negative?

Yes, and double negatives are perfectly correct—and often required—in Portuguese. When a negative word like ninguém (nobody or anybody) comes after the verb, you must use não before the verb. If ninguém were the subject at the beginning of the sentence, you would drop the não.