Dehumidifiers aren't what's thermodynamically impossible, of course; Fontus was just making quantitative performance claims that were thermodynamically impossible about how small their system would be and how little energy it would use.
You don't need to sink to citing YouTubers to figure out how much water air contains. You can just consult a standard psychrometric chart: https://commons.wikimedia.org/wiki/File:PsychrometricChart.S...
You can see from that chart that at, for example, 20 degrees and 30% relative humidity (which, if you're not aware, is pretty dry), you have about 5 mg of water per gram of air, or about 5 grams of water per kg of air, which is about 0.8 cubic meters (1.2 g/liter). So if you want to produce 10 liters of water per day for your family, you need to run 2,000 cubic meters of air through your dehumidifier. (Or a bit more because you can't reduce it to 0% humidity.)
That might sound like a lot, but it's per day, so it works out to 49 cfm, which is not "big fans and lots of power". If we're talking about a 300 mm square aperture it's 260 mm/s of airflow, a breeze you can barely feel, which requires a totally insignificant amount of power compared to the actual refrigeration involved. This is not going to fit nicely on your bicycle like in the fraudulent Fontus videos but it is entirely reasonable as a household appliance.
Solar electricity is free if you aren't using it for something else.
As for bacterial growth and filtering, yeah, that's a real design constraint, and it's one that HVAC systems have fallen down on in the past with disastrous results, but it's not some kind of unsolved engineering problem. Every air conditioner, sea voyage, and water tower deals with it. Here in Argentina just about every house has a rooftop drinking-water tank, where we control bacterial growth with chlorination, by impregnating the tank plastic with bacteriostatic agents, and by making the tanks opaque so algae can't grow. Thousands of years ago, mariners dealt with it by dropping a silver coin in each amphora of drinking water.
It would be a more difficult problem if a dehumidifier were warm and moist, but actually it's cold and moist.
As for the relative costs of tankers and electricity, well, that varies depending on where you are. Around here supply chains are so unreliable that I'd hate to rely on a weekly delivery from a water tanker in order to not die of thirst in 48 hours. (Fortunately, I live a few kilometers from the biggest river in the world. Water is not a problem here, though in places pollution is.)
