To input characters in alphabetic writing systems such as Russian, French and German, you don’t have to install an input method. You can just change the keyboard layout. In X system, this can be done with (Russian, for example)

setxkbmap -layout ru

But I suggest you set some shortcuts before running this command (and change layout via shortcuts). Otherwise, when you have changed to Russian, you may not be able to input Linux commands (in English), which means you cannot change back. Of course you can use mouse to change back if your DE supports it.

To set shortcuts in Openbox, add the following lines in ~/.config/openbox/rc.xml

<keybind key="A-F11">
  <action name="Execute">
    <execute>
      setxkbmap -layout ru
    </execute>
  </action>
</keybind>
<keybind key="A-F12">
  <action name="Execute">
    <execute>
      setxkbmap -layout us
    </execute>
  </action>
</keybind>

After reconfiguring Openbox, you’ll be able to change the keyboard layout via Alt+F11 and Alt+F12.

Finally, there’s a Russian keyboard layout

russiankeyboard