OTA firmwares cannot be restored to. IPSW Downloads collects them for potential future use. They might also be useful if you're doing research.
| ✗ | HomePod | audioOS 9.9.13.2.1 (17B90) | October 30, 2019 | 1.7 GiB | 1220c3e5529674c32ef3c9306e2019ac3a787441.zip |
| ✗ | HomePod | audioOS 9.9.13.2.1 (17B6090) | October 30, 2019 | 1.7 GiB | 1220c3e5529674c32ef3c9306e2019ac3a787441.zip |
| ✗ | HomePod (Unknown Model) | audioOS 9.9.13.2.1 (17B90) | October 30, 2019 | 1.7 GiB | 86af6c34de513cd94b8da512545af40474bcf68b.zip |
| ✗ | HomePod (Unknown Model) | audioOS 9.9.13.2.1 (17B6090) | October 30, 2019 | 1.7 GiB | 86af6c34de513cd94b8da512545af40474bcf68b.zip |