https://wccftech.com/download-macos-big-sur-beta-8/

Apple has released beta 8 of macOS Big Sur to developers. It is available as an over the air update for those enrolled in Apple's beta program.

macOS is always the last piece of software which Apple releases to the public in the full and final form relative to everything announced back at WWDC. With the company releasing beta 7 of macOS Big Sur just last week, Apple is now following it up beta 8.