If you have a mostly sealed environment, such as most modern living spaces, even a low powered and relatively silent peltier dehumidifier can have an impact. A few percentage points can keep dew and mold from forming.

Door sweeps, door shoes, or draft seals can be used to seal the gap between the bottom of the door and the threshold.

In an environment that isn't sealed, such as a room with a gap under an exterior door, then a low powered peltier dehumidifier can't reduce the humidity significantly, because outside air will be continuously mixing with whatever moisture is withdrawn. Water content per volume of air will remain relatively constant. However, most any heater or compressor-driven dehumidifier can have an effect. Heated air from the heater, or heated and dehumidified air from the dehumidifier will have sufficient time and power to affect interior air and surfaces.

In a living space where there is a constant source for increasing humidity, such as a shower or aquarium, less humid outside air can help draw out moisture.

Low cost bluetooth temperature and humidity sensors are available to keep track of indoor and outdoor readings. Their hygrometer function accuracy is limited but still useful. For example, to automate opening and closing of windows, or to turn on bathroom fans, based on the indoor/outdoor humidity differential.

A basement can also increase living space humidity from the surrounding earth if the floor and walls are porous. Even if the basement is treated to prevent water vapor flow, the walls and floors of the basement will likely be cooler than the outdoor temperature, and this coolness causes an increase in relative humidity. Air with the same water content will be higher in relative humidity at a cooler temperature. Click for the thermodynamic concept of relative humidity

Heat absorbed by the surfaces in a room will reduce the local relative humidity. In the case where sealing a room is not possible, such as a garage or room with a missing wall, a radiant heater can reduce humidity. Radiant heaters heat surfaces with infrared radiation.

Interesting unrelated HVAC article: https://www.quora.com/Is-it-possible-to-heat-cool-my-house-by-simply-digging-a-deep-hole-in-my-garage-floor-and-blowing-the-air-up-from-the-hole-using-a-powerful-fan/answer/Erik-Hancock-3