Apple has released iOS 14.0.1 to fix iPhone issues plaguing users since the release of iOS 14. A bug is causing the default browser and mail app to revert to Safari and Mail after the iPhone is restarted. Wi-Fi has been unstable with poor performance and connectivity issues since iOS 14 was released. The new build does not include any security updates. It fixes issues that could prevent camera previews from displaying on iPhone 7 and iPhone 7 Plus. It also fixed issues that prevented images from appearing in the News widget.
Source: https://www.bleepingcomputer.com/news/apple/apple-fixes-iphone-wi-fi-and-default-apps-issues-in-ios-1401/