Back in 2007 they had a 2G cell phone called the Openmoko, which ran Openmoko Linux. You even had terminal access. I would buy an old one, plug it into an old Linux Thinkpad, then add headphones for making calls, then add a ULX3S running custom PHY (TDMA complexity, not OFDMA), then add a LimeSDR PCIe and a receptacle for cat6 ethernet plug-in to laptop. Then add a solar-powered BTS tower w/ OpenBTS/OsmoBTS and Asterisk on Linux. Also, will need to setup OsmocomBB on the phone. Add a sysmousim developer SIM card in SIM reader, plugged into laptop, then write authentication w/ OsmocomBB ports. Then you can call other people, provided they're using OsmocomBB-compatible hardware and read instructions for flashing firmware on the SIM card for self-activation into your free open baseband 2G network. You can even run a computer network over GSM. You'll need a transport-agnostic GNUNet overlay but as a custom BBS scripted in Python w/ installation instructions on the website for how to set-up and connect to, provided they're within range of that tower. Then you name your company (say, Liberty Cellular). You can still make a 2G network even today, provided you have a part 5 experimental radio license from the FCC and took training courses. While implementing TDMA on FPGA (ULX3S) may be a significant engineering effort, you can still learn that in these FCC classes on how to script custom TDMA, et cetera.
under socialism we will be restoring the 2G and 3G networks to bring millions of devices back online as part of our degrow consumption and grow employment 5 year plan
You can install regular (non-Android) Linux on many modern phones:
https://postmarketos.org/