https://wccftech.com/download-ios-15-and-ipados-15-beta-without-a-developer-account/

You can download iOS 15 and iPadOS 15 beta updates for iPhone and iPad without a developer account. Here are your options.

iOS 15 beta and iPadOS 15 beta are out there for everyone to try out. Well, not exactly everyone. As long as you subscribe to Apple's Developer Program, you can download the beta bits and install it onto your compatible iPhone and iPad.