The first experimental build for the 10 series was 2025120400. It took nearly 4 months for the 10 series to be supported.
The first release supporting the 9 series was 2024083100, released about two weeks after the 9 series was announced.
Supporting a new device can be relatively quick, but can also take significantly more time, depending on how Google decided to ship the software on the new phones. For example, in the past, new Pixel phones were shipped with an OS based on an older quarterly release of Android, which necessitated they had a special device branch in GrapheneOS, which can be quite a hassle to bring up and maintain.