I can't even use the Prime Video apps, because they all ignore all language settings (both those of my devices and my Amazon account) and pick which language to

I can't even use the Prime Video apps, because they all ignore all language settings (both those of my devices and my Amazon account) and pick which language to use based on IP Geolocation. There's a setting for language on the web, but it only affects web. In my case I'm a foreigner who is still learning the local language, but it must be a real nuisance for people in multilingual countries like Belgium or Switzerland where I guess it would just go "oh, Swiss IP, I guess you want German then".