audioOS 9.9.15.1 (build 19J572) is an official Apple over-the-air update for the HomePod, released on 2021-10-25T17:12:16Z. The update package is 1.22 GB. This is a delta (partial) update that requires 13.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 54f71953cc80824887933841b8b0d507c18a6ff7.zip.