I finally have a proper prototype running the same (mostly) hardware that the final phone will be running on! The prototype doesn't have a cellular modem thanks to the lack of properly priced SIM7600 breakout boards, but the devkit will have a modem. This version does have a screen, a keypad, and both CPUs - one for processing and one for interfacing with the display. Sorry I had to post a video, Hackaday just throws errors when I try to upload pictures.