I leave a 5-gallon $2.98 BORG bucket (Big Orange Retail Giant) at my off-grid property. Fill it with lake water, add laundry detergent, and use a thick blunt stick as a stirring / punching tool. It works fabulously. Homer rules.
IMO, the laundry challenge with a B is not the washing - anyone with arms can accomplish that (even many disabled persons). The real challenge is drying. I've got an under-awning portable rack designed on paper thus far, and hope to make it a fabricated reality before next summer's camping season.
An ideal rack fits under the awning so that the clothes don't get rain sprinkled (my property is on the far northeastern coast of Nova Scotia, where it rains more often than not).
PLUS - and here's the kicker - it affixes magnetically to the side of the van. Ideally, its down-rods would fit between my side windows which is why I cannot buy or adapt an existing consumer product. Nothing fits the space.
I already dry clothing on the side of the van using magnets to hold the pieces, but I'm aspiring to create a more efficient apparatus. An ideal rack would be higher than most of the clothing pieces shown here. Once they are below the windows, even gently blowing rain can reach them.