Learn Russian: Ни одна афиша не висит на улице. - There isn't a single poster hanging on the street.

Yes, and that is required in Russian. When you use an emphatic negative phrase like ни один (not a single), you must still negate the main verb using не. Without не, the sentence would be grammatically incorrect.

Why is the feminine form ни одна used here instead of the default ни один?

The phrase ни один must agree in gender and case with the noun it modifies. Because афиша (poster) is a feminine noun acting as the subject in the nominative case, we must use the feminine nominative form ни одна.

Could на улице be translated as 'outside' in this context?

Absolutely. In Russian, на улице is the standard and most natural way to express 'outside' or 'outdoors.' The sentence can perfectly translate to 'There isn't a single poster hanging outside.'

Why does Russian use the verb висит (hangs) instead of just saying the poster 'is' there?

Russian frequently requires specific verbs of spatial position—such as standing, lying, or hanging—where English would simply use the verb 'to be'. Because a poster is attached to a vertical surface, it physically 'hangs' (висит).