I agree with standard dehumidifier. I run one in the kitchen of the motorhome with the drain down the kitchen sink. Since the gray water tank was empty after the last trip, I just leave the valves open so that the water drains through the gray water tank and drips out on the gravel parking area.
One minor consideration if you are in an area with frequent power failures. Some electronic control dehumidifiers lose their settings during a power failure and will not resume operation when the power is restored. Look for a unit that retains settings and will resume operation when the power is restored.
The older, non-electronic control types will resume operation after a power failure also.
Fred