Android announced the release of Developer Preview 9 for the Privacy Sandbox on Android with API and SDK improvements. 

The initial release of Custom Audience Delegation introduces the ability to create custom audiences for buyers without an on-device SDK. It also integrates with Bidding and Auction services for more intricate ad auctions. 

Enrollment is no longer obligatory for using the Attribution Reporting API for development and testing, while debug reporting enhancements involve extra detailed reports and app-to-web debug reports. 

The SDK Runtime can now initiate intents in other apps and connect with approved service allowlists.

In conjunction with Developer Preview 9, Project Flight has been introduced. This initiative encompasses a series of sample applications that collectively demonstrate the practical application of Privacy Sandbox APIs within real-life user journeys. 

Included in Project Flight is an advertiser app showcasing a conversion scenario through the booking of a travel experience, a publisher app illustrating the display of relevant advertisements and the recording of associated events, and an SSP library highlighting the functioning of ad selection procedures and source registration.

Also included are an MMP library, presenting the integration of custom audiences and trigger registration, and a mock server backend. Additional details on the latest preview are available here.