I was suggested I will more than likely will not be able to install custom dictionaries on iOS
https://www.mobileread.com/forums/sho...d.php?t=256469
Then the question is - I was not able to find an answer in Google -, what is the name of the dictionary (Merriam Webster, Oxford, etc.) provided by Apple in major markets (UK, US, Germany, for example), and how do I change locale if I want to change between these provided dictionaries? As the devices are not country-coded.