Huawei’s HarmonyOS is seen as the only credible challenger to Android and iOS in the mobile operating system duopoly, even though the prospects of this third-horse outsider will be limited almost everywhere except China. However, if you look hard enough, you can just about make out another horse coming up the rear, in the form of KaiOS – a Hong Kong-based outfit founded in 2018 with ambitions of stealing market share from Android in developing regions. Given this target market, hearing that the Linux-based KaiOS is making strides in the US, riding a wave of rising video app usage on the platform, therefore caught us off guard. This comes in the form of a partnership with multi-cultural on-demand programming provider…