[timschumi]

GrapheneOS only supports devices that are still supported by the OEM, and they generally seem to have very few modifications that touch on frequently-changed parts of AOSP. In short, they can be relatively certain that nothing will break when they rebase, Google does the work for them.

On the other hand, LineageOS runs a lot of devices at the very (lower) edge of compatibility, which means that (with Google pushing large changes quarterly instead of yearly) the build roster has to be reevaluated quarterly instead of yearly as well. This was not anticipated properly for the Android 14 (LineageOS 21) cycle, which resulted in 19 devices not being able to be built on a previously supported major version (and therefore dropping from the roster completely).

In addition, the components that have been causing rebase conflicts each year now have the opportunity to cause rebase conflicts multiple times a year.