Learn French: Je me doute qu'aucune galerie ne vend cette imitation. - I suspect that no gallery sells this imitation.

Because the main clause uses se douter que (to suspect that), which expresses a strong belief or probability. Even though it looks like douter que (to doubt that) — which does trigger the subjunctive — the reflexive version se douter que takes the indicative.

Does se douter mean "to doubt oneself"?

No, se douter is an idiomatic reflexive verb that means "to suspect" or "to imagine". It expresses the opposite of douter (to doubt), which is exactly why it doesn't trigger the subjunctive.

Why is there a ne before vend but no pas?

The negative word here is aucune (no / not any), which pairs with ne to form the negation ne ... aucun(e). When you use negative words like aucun, personne, or jamais, you must drop the pas.

How does the word order work with aucune here?

In this sentence, aucune galerie is the subject of the dependent clause. When aucun(e) is part of the subject, it comes at the beginning of the clause, followed by the noun it modifies. The ne is then placed immediately before the verb: aucune galerie ne vend.