Twitter rival Threads — the Meta-owned app seen as a major rival to Elon Musk’s troubled microblogging platform — already has 30 million signups, Meta CEO Mark Zuckerberg said Thursday morning. The newest addition to the Meta line of web-based products debuted with a bang. The much-hyped application, already dubbed the “Twitter Killer app,” officially launched Wednesday night. About two hours after that, 2 million people had already signed up for it, Zuckerberg shared in his third-ever post on the platform. A few hours later, the Facebook co-founder went back on the site to announce 10 million...