https://wccftech.com/apple-seeds-beta-7-of-macos-big-sur-to-developers-download-now/

Today, Apple has seen fit to release beta 7 of macOS Big Sur to developers for testing purposes. The new build arrives two weeks after the beta 6 was seeded to developers. If you're a developer, you can download the latest beta on your compatible Mac right now.

You can grab the latest macOS Big Sur beta 7 from the Apple Developer Center. Make sure to install the appropriate profile and if you have the beta 6 installed already, the new build will be available through the Software Update mechanism in System Preferences.