Reverse osmosis desalination is a very costly way to produce fresh water from seawater, plus it comes with a variety of problems such as what to do with the filters that need replacing often, these systems need lots of energy (typically electric) to create the high pressure to get the seawater through the filters and the problem of the large amount of high salinic water or brine produced by the process that is an environmental hazard often just dumped back into the sea.
The better solution is to use the sun's heat to produce water vapor. Then condense the vapor back to distilled water. The condensation can be done by freezing seawater in large flat underground facilities taking the layer of ice that first forms on top of the seawater which is largely salt free and moving it to V shaped tanks where as they melt the vapor from the sun heated seawater condenses on the outside of the tanks.
The water harvesting on the outside of the tanks can be sped up with a windshield wiper like device that scrapes the pure condensed water off the outside of the V tanks or you can just let it drip off using less energy.
As the ice melts it fills the V tanks with cold pure, mostly desalinated water. That water can then overflow and be mixed with the condensed water. This can all be powered by photovoltaic solar panels to run the heat pumps to freeze the water. Solar water heaters like the one pictured above can be used to heat up the seawater. You can keep heating the brine until all you are left with is nearly dry salt. You can move this salt to existing salt flats that have been deteriorating because of climate change.