As I understand your neighbour wants to remove fluoride, can he get an under tap filter that only removes those types of chemicals? If not, why not simply buy mineral/spring water. Where I live it's the same price.
Kdenlive is likely your best bet. Even if u have issues here and there, in the long term you'll be happy you stuck with it. It has very active development and is shaping up to be the most used foss video editor.
Bucky was right once again with his theory of "Ephemeralization" https://dbpedia.org/page/Ephemeralization ... The only reason we're concerned with these companies employing Devs and spending Billions to do what small teams of FOSS are able to achieve is simply a bad economic system that requires "make work" or Bullshit jobs for wages to feed the parasite class, instead of us living like the Jetson's. Time to move one!
Bringing peace is surprisingly lucrative -- for weapons contractors, black rock and now the mining industry, huh 🙈