RE:Dallar ;Trevali reports in USD, so all numbers from their different operations convert to USD. I would expect that when they sell their offtake to Glencore, they are paid in USD as well.
That means, at a local scale, they pay their employees in money converted from USD, so the weaker their local currency is relative to USD, the more bang they get for their buck.
However, the majority of their expenses are in CoGS, and the majority of the CoGS is in smelting fees and mine operating expenses. I would bet that only a small amount of that comes from actual salaries to their miners - that would be the only place they would actually benefit or suffer from exchange rates.