Your system information

• Steam client version: 1460023329
• Distribution (e.g. Ubuntu): Ubuntu Linux 16.04 LTS
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes

As you know, we can not type Korean, Japanese and Chinese.
But recently i found the way to type CJK(Chinese-Japanese-Korean)!!

First, you must install the packages listed below.

libsl-ttf-gsf
libsdl-ttf2.0-0
libsdl-ttf2.0-dev
libsdl1.2-dev
libsdl1.2debian
libsdl2-2.0-0
libsdl2-dev
libsdl2-gfx-1.0-0
libsdl2-ttf-2.0-0

After Installing, Start or restart your steam client.
Finally, Click Controller Icon (Right-top side) to enable Big Picture mod!
Now chat anyone with your prefer language.

As you can see. i can type korean!

Another Picture! You can type English and Korean.
But I don't know why i must enable Big Picture mod to type CJK..

Because CJK typing only available at Big Picture mod...
I think Valve have to fix some part...