https://wccftech.com/download-apple-seeds-beta-8-of-macos-big-sur-11-3-to-developers/

Apple has seen fit to release beta 8 of macOS Bug Sur 11.3 to developers for testing purposes. The new beta build arrives a week after the release of beta 7 to developers. Moreover, Apple has also seeded beta 8 of iOS 14.5 and iPadOS 14.5 to developers. For now, let us see if Apple has added any forward-facing addition in the latest macOS beta build.

If you are a developer, you can download the latest build from the Apple Developer Center. All you have to do is use the Software Update mechanism in System Preferences once you have installed the appropriate configuration profile from the Developer Center. macOS Bug Sir 11.3 beta 8 is available on all compatible Macs.