I couldn’t find the topic like that by search on “English input katakana” keywords.
I am using an Android mobile phone with SwiftKey keyboard. The matter is, that if I am using English layout to enter the reading the first symbol is always converted to katakana while all the other to hiragana. The answer is not accepted by the system. So I have to switch to the Japanese layout of the SwiftKey to enter hiragana every time when I need reading and back when I need meaning. That’s not a big deal for me for the current moment, but I believe this still is a bug worth mentioning.
That’s the screenshot