You can use any portable air conditioner in an RV, though some work better than others in particular weather situations.
Ventless portable air conditioners use humidity to cool the air and only work well in dry climates. This style would not be a great choice for those who already battle humidity in their RVs.
A vented version will typically require a hose attached to drain the excess moisture collected as a part of the process. Some vented options have auto-evaporation that will attempt to evaporate the moisture into the exhaust air.