SpartanUI
SpartanUI has historically used Cognosis as its font and has poorly performed for multiple languages. In the latest builds of SpartanUI the addon is has moved to Goggle's NotoSans, while the new font NotoSans does a very good job of covering most languages (Over 30 Languages in 1 file). The Simplified Chinese character set is separate in order to keep down the file size. In order to do the same with SpartanUI the chinese font has been split off into its own addon.
When you run this addon it will automatically tell SpartanUI to use the Chinese font file if your World of Warcraft client is set to Simplified Chinese.
Your Feedback is needed
My Client does not run in Simplified Chinese so i can only test this add on so much, let me know if you have issues. or of it works perfectly.