Xiaohongshu’s biggest shareholders are in talks to sell shares in the Chinese Instagram-like service at a valuation of at least $20 billion, drawing interest from Tencent Holdings Ltd. and other big names as a potential TikTok US ban approaches.Backers GGV Capital, GSR Ventures and Tiantu Capital are negotiating to sell part of their holdings in China’s closest parallel to Instagram, according to people familiar with the matter. Funds that showed interest included existing stakeholders HongShan ...