I'm making a replacement motherboard for the Nokia 1100 that runs Linux and supports LTE. I have the software working well on a MangoPi dev board and I've designed two PCBs: one "test fit" board that just breaks out the phone keypad/LCD to pin headers, and the actual board with everything on it. Now I just need to order the PCBA which is super expensive :)
It uses an allwinner T113-S3 SoC and the Quectel EC25 LTE module, and I've made sure voice calling works over LTE, at least on T-Mobile in the US. (this is tricky bc of carrier rules)
video and photos of MangoPi test setup and my board layout here: https://constcast.org/n1100c/
Interesting.. May I ask why pick such a simple model of Nokia if you'll tinker with it? Just to learn?
I wanted the challenge of trying to fit all the components into the small board area available (this phone is tiny), and I liked the idea of creating an updated version of the best-selling cell phone of all time. I figured some of the "dumbphone" crowd might be into it too, if my design works I might make them available for sale