The portions of SailfishOS specific to it including the user interface and application layer are nearly entirely closed source, unlike the open source Android Open Source Project (AOSP). SailfishOS has far worse privacy, security, functionality and usability than the Android Open Source Project. It isn't possible to make a fork improving it due to it not being open source like AOSP.

You can run desktop apps on GrapheneOS including on a desktop monitor via the desktop mode with free form windows. There's support for non-native apps via hardware-based virtualization. These features are experimental but already work pretty well.