China’s cyberspace watchdog has unveiled new draft rules that will make it harder for Big Tech firms like Tencent Holdings and ByteDance to profit from video gaming, live streaming and social media services targeted at the country’s 180 million internet users under the age of 18. The new draft regulation, published by the Cyberspace Administration of China (CAC) on Monday, marks the latest effort by Beijing to shield minors from internet services. China has already banned profit-making in off-campus tutoring to reduce the burden on students, and has limited video game playing time to three hours per week for teenage...