By default latest "stable" Debian 9 does not have any means of multilingual support.
It is installed only in pre-selected language with only one simplest direct keyboard input.
There are some manuals how to add more locales using console (which nulifies all the efforts of GUI building by itself), and even foreign keyboard layout can be added with minor problems in layout switching.
But there are languages, like Chinese and Japanese requiring special input method (IME). And there is nothing in Debian, offering smooth integration of Asian input along with european language inputs.
I.e. there are many system manuals for iBUS and fcitx. There are some manuals on installing iBus, and no working manual for installing fcitx on Debian. At least I could not get any success installing fcitx on Gnome.
Worse.
Installing iBus on KDE results in total input damage. Input becomes near disabled, you have to type "ddddddeeeeeebbbbiiiiiaaaannnn" in order to get "debian".
In Gnome iBus (lets use a manual like this http://okomestudio.net/biboroku/?p=2472) have almost no effect on input. Almost means - you loose your secondary keyboard layout, while the indicator is still working.
I just have no idea how to install English, Georgian, Russian, Japanese, and Chinese simultaneously with one switch hot-key in Debian.
It is very simple in Windows. You just install new inputs, and the system decides whenever just change the layout, or activate Japanese IME, etc. You can even have handwriten glyph recognition there.
It is much simpler iOS, just add the input, and push the selector button in your application.
But why not in Debian?
Or is there any step-by step manual for installing all these inputs with one indicator and one hot-key switch?