Most Larger RVs 32ft + have been pre-plumbed and pre-wired for Washer/Dryer since 1994. Chances are you will find a recent model with or ready for a washer/dryer.
We have a stacked Maytag set in our RV. It comes in handy.
However, many private campgrounds have laundry facilities which provide a way to clean clothes plus the advantage of socializing with other campers as they do their laundry.
There are several countertop washers some electric and some hand crank. These work well and will keep up with the clothes two adults use. Just hang the clothes up in the shower or outside (if allowed) to dry.