PostmarketOS compared to other distributions
There was once a Ubuntu Desktop port to the grouper, but it was slow and not very usable. It is however compatible with desktop Ubuntu apps.
LineageOS is an Android derived open source project. It runs the Android framework.
Arch Linux is minimal Linux installation with a larger focus on offering the newest software rather than a stable experience
Ubuntu Touch uses Halium, built from Android libraries. The only UI is Unity 8, however on most (all?) devices calls work.