Billionaire Elon Musk said that he was not interested in purchasing TikTok, the popular short-video app that the United States has been trying to ban over national security concerns with its Chinese owner ByteDance. Musk’s comments, made in late January, were released online Saturday by The WELT Group, a part of the German media company Axel Springer SE, which hosted a summit, where the Tesla chief joined the conference via video. “I have not put in a bid for TikTok,” Musk said a week after U.S. President Donald Trump said he was open to Musk buying the ByteDance-owned app if...