@wire I follow another project aiming to design a phone. The focus is not at first on privacy and security, but since it is open-source, and partially open-hardware (I'm not sure exactly, but it is mentionned that the connectors all have open-source software). And this phone will quite cheap, although not featuring everything that a smartphone has, it is more than a "dumbphone" : https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone