For the desktop PC that you use ethernet cable for all connections (IP over DHCP), and that includes a 3D printed plastic enclosure for the router and 2G cellular modem radio box, as well as over the SBC made from homemade printed circuit board via the toner transfer method, with soldering equipment for the Lattice ECP5 FPGAs for the UberDDR3/custom DDR3 (PhD-level work), VexRiscV chips for the cores, bigger open source FPGAs for the MIAOW GPUs (similar to the older AMD chipsets), MCUs for the battery (Li-ion or Li-Po), maybe hardware killswitches, with USB cord attached to SBC box via USB port flashing Guix system onto the monitor (use a Modos paper display) and add a keyboard/mouse (keyboardio for the keyboard and Ploopy kits for the mouse). Now you have a desktop PC/cell phone 2-in-1. And if you want, you can even make a PDA/softphone using VexRiscV cores, DDR3 FPGAs, and so on with a resistive touchscreen and touch pen. That is wired to the olinuxino router box that is wired to the default ISP hardware. Use Guix + Wayland (Sway) for the mobile UI. Use Jami or GNUNet CADET for VoIP softphone applications, use custom proxies written in Python with X25519, Poly1305, ChaCha20, and Kyber fir cryptographic post-quantum emcryption, make it SOCKS5 for better location barriers, use rkhunter, clamav, kvm/qemu, iptables, firejail, pyshark and GNU Icecat with LibreJS for security.