GrapheneOS is the security-first Android distribution. It tends to drop support for older devices not long after official driver updates stop, because it's harder to ensure top-notch security in that case. The Pixel 5A is in "extended support", which is to say deprecated.
LineageOS is the broad-support Android distribution. Its current version supports all Pixel devices. Third parties have even built recent-ish versions for ancient devices (e.g. Android 13 on the Nexus 5).