A highly efficient multi-stage solar still has been developed at MIT [1].
An alternative to desalination is capturing humidity from the air, e.g. by isothermal membrane-based air dehumidification [2] or passively using condensation [3].
I’m involved in building a fund to invest in startups in this and other areas related to biosphere resilience, and would love to get in touch with people taking such technology to the market.
My guess is we will be needing adaptive measures sooner than most people expect.