On camera, Li Ziqi, one of China’s most darling vloggers, lives a peaceful, enviably pastoral life. In one video , Li spends her morning riding through a misty forest on horseback, collecting magnolia flowers in a wooden basket. Dressed in a sweeping red cape, she looks like a cross between a Disney heroine and a mythological Chinese princess — something that taps into a current craze for traditional hanfu clothing, popular among young people nostalgic for a simpler, pre-industrial past of rites and etiquette. At her Sichuanese countryside home, off the grid and entirely self-sufficient, there are no signs of...