The below content is copied from Amazon release notes:

Improvements to the online inventory report
We’ve introduced two improvements to the online inventory report: First, multi-select breakdowns now allow you to group supply source and domain/app ID metrics in the same report. Second, you can now download inventory report data to Microsoft Excel and analyze it offline.

Amazon viewability targeting is now available for mobile line items
Amazon viewability targeting is now available for Amazon mobile display and mobile app line item types. This feature offers five viewability tiers (70%+, 60%+, 50%+, 40%+, and up to 40%).

Feedback on creatives rejected by Xandr (AppNexus) and Google
Creatives that run on Xandr (AppNexus) and Google Ad Manager supply are subject to manual and automated audits conducted by those exchanges’ creative audit teams, and may be rejected resulting in creatives not delivering impressions on those supply sources. With this update, you can now see Xandr (AppNexus) and Google creative rejection reasons alongside the creative audit feedback we provide.

Third-party pre-bid targeting from DoubleVerify, Integral Ad Science, and Oracle Data Cloud
Pre-bid capabilities from DoubleVerify, Integral Ad Science, and Oracle Data Cloud are now available. With this change you can now filter third-party ad inventory for invalid traffic, viewability, and brand safety and provide better control over where your ad is delivered. Billing is currently not available for third-party targeting and filtering. For more information, refer to this help article.

Amazon audience pricing
On January 1, 2020, we updated pricing for Amazon audiences used in Amazon DSP display campaigns. The Amazon DSP audience fee is a cost per thousand impressions, or CPM, applied to Amazon audience segments. For more information, please visit the January section of the DSP help center release notes.