it really isn't so miraculous to "build" a cellphone.
various gsm cards/chips exist, the rest is software.
what is hard is to build a usable "smartphone".
i don't know if the above chip is compatible with pine64.
probably not.
looks like it doesn't require a motherboard at all:
https://learn.adafruit.com/assets/17732
but, like i said, various GSM cards/chips are available for all sorts of architectures.
i guess even a usb dongle could be made to work.
various gsm cards/chips exist, the rest is software.
what is hard is to build a usable "smartphone".
i don't know if the above chip is compatible with pine64.
probably not.
looks like it doesn't require a motherboard at all:
https://learn.adafruit.com/assets/17732
but, like i said, various GSM cards/chips are available for all sorts of architectures.
i guess even a usb dongle could be made to work.