Dynamic font only changes the visualization of the font, so if input doesn't work with it for some reason, chances are standard font won't work either. Does it? Make sure the TTF you chosen actually has the glyphs. Most fonts don't have asian glyphs in them.
Well, I'm using Korean Font. It has English, Korean Glyph and Tested following:
1. Typing English in UILabel from Inspector (Editor, Play Mode) => OK
2. Typing English in UILabel inside UIInput from Inspector (Editor, PlayMode) =>OK
3. Typing English in UIInput (PlayMode) => OK
4. Typing Korean in UILabel from Inspector (Editor, Play Mode) => OK
5. Typing Korean in UILabel inside UIInput from Inspector(Editor, PlayMode) => OK
6.Typing Korean in UIInput ( PlayMode) => Fail
Fail Means, any Charactor added nothing.
UILabel works fine every situation. May be font looks not problem..