GSI (Generic System Image) ROM-s do have bare-bones apps due to their nature of being mostly designed for developers. That won’t really be a problem as you can just install better alternatives to those apps. The problem with these ROM-s is that they most likely won’t have drivers for the camera for example. Also the phone has to be Treble-compliant and it has to come with Android 9 (ie. it has to be preinstalled, devices that have been upgraded to Android 9 aren’t supported.)