Apple has made the third public betas of macOS Big Sur 11.3, iOS 14.5, and iPadOS 14.5 available for download.
Those who wish to participate can download the latest betas and configuration profiles from the Apple Beta Software Program. Subsequent changes for existing participants are available as over-the-air updates on enrolled devices.
The third developer betas of iOS 14.5 and iPadOS 14.5 contained a new tab in the Find My app for "items." This tab will be used for third-party tracking devices that use Apple's system and eventually will be populated by "AirTags."
AppleInsider, and Apple itself, strongly advise users don't install betas on highly-important or primary devices, due to the potential for data loss or other issues. Instead, it is recommended to install betas onto secondary or non-essential devices and to ensure there are sufficient backups of important data beforehand.
Update: Apple has also released a third version of the tvOS 14.5 beta to public testers.