https://wccftech.com/download-latest-ios-15-beta-7-without-a-developer-account/

You can go right ahead and download the latest iOS 15 and iPadOS 15 beta 7 without a developer account at all.

Apple seeded the seventh beta of iOS 15 and iPadOS 15 to registered developers with an iPhone and iPad just yesterday. But, if you are a non-developer and want to try out the newly released software, then you can go right ahead and install it.