您可以使用反向代理（如nginx）来解决这个问题。通过使用nginx，您将能够根据请求来自的域将请求重定向到正确的应用程序。
pseudo nginx配置：

server {
        #your other config....

        #redirect all request from your.domain.com to your wordpress app.
        if ($host = your.domain.com) {
            #redirect traffic to wordpress upstream
        }

       #redirect all unsecure www to secure www
        if ($host = your.sub.domain.com) {
            #redirect traffic to flask upstream
        }
    }