I have worked quite extensively on the PinePhone, though only for my own purposes. Have been dogfooding my own system for months as a daily driver, and have implemented quite a lot of things, except for one thing: voice calling.
Even Google and Apple have problems getting that 1 thing working reliably (even though half of smartphone is supposed to be a phone) - I don't even try to take a stab at it. There is some serious bug every once in a while, which sounds so ridiculous... I just carry a dumb Nokia for calls, and for everything else, I can use my slab (assuming its battery is still not dead)