I find myself referring back to this reddit page to configure Japanese input on fresh elementary OS installations but it's closed and cannot be edited to include other language inputs:
Is it possible to add this to a Wiki post? (with appropriate attribution to the OP on reddit)
To quote from the Reddit post:
The best working method is to use fcitx input method framework. The following description is suitable for many different languages, including chinese (pinyin, bopomofo aka zhuyin or chewing, etc.), japanese [anthy, mozc], etc.
Time to open up your terminal: Ctrl+Alt+T
sudo apt-get install software-properties-common
sudo add-apt-repository ppa:fcitx-team/nightly
sudo apt-get update
sudo apt-get install fcitx fcitx-config-gtk fcitx-table-all
Chinese: sudo apt-get install fcitx-sunpinyin fcitx-googlepinyin fcitx-module-cloudpinyin fcitx-chewing
Japanese: sudo apt-get install fcitx-anthy fcitx-mozc
sudo apt-get install im-config
im-config
Commands for Japanese:
sudo add-apt-repository ppa:fcitx-team/nightly
sudo apt-get update
sudo apt-get install fcitx fcitx-config-gtk fcitx-table-all
sudo apt-get install fcitx-anthy fcitx-mozc
sudo apt-get install im-config
im-config
Commands for Chinese:
sudo add-apt-repository ppa:fcitx-team/nightly
sudo apt-get update
sudo apt-get install fcitx fcitx-config-gtk fcitx-table-all
sudo apt-get install fcitx-sunpinyin fcitx-googlepinyin fcitx-module-cloudpinyin fcitx-chewing
sudo apt-get install im-config
im-config
In the window that opened after you typed im-config, the second line shows which input method is currently in use on your system. If might be : ibus, scim, xim or whatever else. If it shows "missing, default, cjkv or auto" remember it and click "Ok".
-> If at step 6, the line Currently in use on your system was different from "missing, default, cjkv or auto", click yes and select fcitx input method in the window that will open then click on "Ok".
-> If at step 6, the line Currently in use on your system was "missing, default, cjkv or auto", click on "No".
Last windows Click "Yes" ;-).
Open "System Settings" -> "Language Settings" and click "complete installation". Change settings as you wish for date formats and so on then click "Set Language".
Restart your computer.
hell
You will see a new icon on the right up corner that allows you to choose your input.
To add wanted inputs :
Click on Configure
In the new window, click on the plus at the bottom left corner.
Untick "Only show current Language"
Search your favourite input method by name. For example : pinyin, chewing, anthy, mozc, etc.
Select it and click Ok for add it
Open any window, hit ctrl+space (default trigger) to switch language and enjoy !
Other configuration options are available such as changing the Triggers, e.g. to switch between English and Japanese or between Hiragana (ひらがな) and Katakana (カタカナ).
Many options are available from the input switcher icon in the right top corner icon's menu.
As it took me a very long time to find this out, I wanted to share it with everyone.