I have Mobian installed, and I don't have a spare SIM card to try calling and SMS. (I have tried postmarketOS and kde neon, and neither was good enough)

Functionally, everything else works: WIFI, apps, suspend, camera, music, etc.

I wouldn't use this as my primary phone, though, as it still crashed on me a few times. Many programs cannot adapt to the screen size effectively; buttons, menus are sometimes not possible to see.

It's not unusable, but not ideal if you want a robust primary phone.

Another drawback (if used as a main phone) is that it's really slow. In fact, it's possibly the slowest device --- with regard to user interaction --- that I have used in years, which is okay for a pinephone, as it is intended as a testing device.