The energetics of a solar still aren't really attractive. It takes about 600 calories to vaporize a gram of water which is then condensed back to liquid. True, some of that heat could be diverted to the heating process of getting water from ambient temperature up to the vaporization temp..
The heating to boiling only takes 80 to 100 calories per gram, depending upon the initial starting temperature.
The solar heater to heat to just below boiling then too would take only about this much energy. So, the simple heating/sterialization process could perhaps give you nearly six times the treated water as the solar still - for the same amount of captured solar energy.
Recently, I was party to a discussion on distilled water, and the bother and cost of buying it. Yes, someone brought up the idea of a solar still. Then someone else got some data on small affordable commercial solar stills and the amount of distilled water you could easily generate from a sunny window wasn't very much. The discussion just tapered off to nothing after that. I believe that people just went back to the bother and cost of buying distilled water in the relatively small quantities needed, about a cup or so per day.
I was initially excited about the use of solar UV as a water treatment, and still have an interest.