Just as a desktop version, #mobilenixos supports building qemu images of the system. As far as I understand, the hardware-correct #pinephone emulation does not exist, so developers use uefi-x86_64 as a not-that-far match. I suppose this kind of emulation is good enough for testing system services and may also help to get an idea of possible screen issues.
Tech notes on running the phosh mobilenixos configuration https://github.com/grwlf/mobile-nixos-cfg#running-the-phosh-config-in-a-qemu-emulator
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