Last year, after nearly a decade working long hours at a variety of factory and office jobs in Shenzhen, one of China’s tech-saturated mega cities, 28-year-old Yu Lixia came home to Jitian, the remote village where she grew up. She started a modest online shop selling local specialties such as tea and wild mushrooms to customers near and far.

Ms. Yu’s decision to return to her rural roots would have been surprising just a few years ago, when hundreds of millions of people were fleeing China’s small towns in search of good jobs and excitement in cities. But cheap smartphones and a government push to bring affordable internet access to poor areas are changing how rural residents spend their time and money, and creating new opportunities that are drawing some transplanted city dwellers home. The trend, while still small, is opening up new markets for internet giants Alibaba, ByteDance, Tencent and others whose social media, payment and e-commerce apps are driving the change.