Steam Prison now supports Simplified and Traditional Chinese! You can change the language from the config menu in game. Also accompanying this update, the game has been ported to new program to support the new languages and to fully combine the DLC with the main game. However due to this change, your old save data from the base game will no longer be usable. If you prefer the old build of the game, it can still be accessible by choosing the original_build beta branch from the properties menu.