Pixel 5 should only be used to preview what GrapheneOS provided prior to October 2024 when Android 15 was released and we migrated to it. It's an end-of-life device and therefore lacks driver and firmware updates. We were able to provide some of those updates past the end-of-life, but not most, and we recommend against using it. We show a notification about it being an insecure device at boot. We continued providing all of our updates and the Android updates for it until the release of Android 15, at which point we shifted to supporting it via a legacy extended support branch based on Android 14 QPR3 with backported AOSP patches and minor fixes of our own. Our support for the Pixel 5 has been winding down further since it's increasingly insecure and we don't want people to use it based on us still providing updates. A Pixel 5 works as a way to try out outdated GrapheneOS but that's about it.
Using GrapheneOS on it would be more secure than the stock OS but it's going to be quite insecure regardless of the OS so we'd recommend just not using it. The intention of our extended support prior to Android 15 and then legacy ex trended support following Android 15 was harm reduction for people unable to afford a new device yet. That's essentially over now. We just didn't remove it from the site yet to avoid complaints. It informs people that it's an insecure device at boot so it's better than people getting misled into believing the alternate OS they've put on it keeps them safe when it doesn't.