Learn Italian: Nonostante il ghiaccio sia pericoloso, andranno avanti. - Even though the ice is dangerous, they will go forward.

The conjunction nonostante (even though / despite) introduces a clause of concession. In Italian, this type of conjunction requires the subjunctive mood. Since the ice is currently dangerous, we use the present subjunctive sia.

Could I swap nonostante for sebbene or benché in this sentence?

Yes, they mean the exact same thing in this context. You could say Sebbene il ghiaccio sia pericoloso or Benché il ghiaccio sia pericoloso and the meaning and grammar remain exactly the same.

Can you use nonostante directly with a noun, like "despite the ice", without a verb?

Yes! Nonostante is very versatile. You can use it as a preposition followed directly by a noun, like nonostante il ghiaccio (despite the ice). In this sentence, however, it is used as a conjunction introducing a full clause with a verb, which is why it triggers the subjunctive.

The main verb andranno is in the future tense, but sia is in the present. Is it normal to mix tenses like this?

Absolutely. The main action of going forward is happening in the future, so we use the future tense andranno. The condition of the ice being dangerous is true right now, so the present subjunctive sia fits perfectly.