Hello! My webbrowser has set ‘Accept-Language’ to 'zh-CN,zh' by default, and https://guix.gnu.org will return 404. I have tested with curl, 'zh-CN,zh', 'zh-CN', 'zh-cn' is 404 while 'zh', 'zh_CN' is 200.
The first time I found it is on 2021-02-23. And it didn't happened about one or two months ago. I think there may be something wrong with the web server.