https://wccftech.com/download-beta-4-of-ios-15-and-ipados-15-released/

Beta 4 of iOS 15 and iPadOS 15 for iPhone and iPad devices is now available for download if you are a registered developer.

With the release of iOS 14.7 and iPadOS 14.7 last week, we knew that this particular week will shed light on a new iOS 15 and iPadOS 15 beta. So, if you were excited to test out beta 3 of Apple's latest software, then you will be pleased to learn that you can now update to beta 4.