Hi there,
Minitek Smart Search is based on Joomla Finder component (Smart Search). Both are using the Joomla Smart Search engine. The engine currently has some limitations when it comes to multibyte characters (such as Chinese or Japanese).
I have created a hidden menu item in your site for the Joomla Smart Search so that you can test the search terms.
https://台南市營登地址.com/ss
You will see that you will get the same results in both Minitek Smart Search and Joomla Smart Search. If the Joomla Smart Search component can't find a result, then Minitek Smart Search will not be able to find it either.
One thing you can do is to make sure that your database tables collation is set to UTF-8. Otherwise the Smart Search engine will not be able to search chinese characters.