If we're talking cyberpunk dystopias, we'd have to resort to hand-soldered audio couplers that use our locked-down phones as modems. Once the next Android/iOS update detects and blocks unauthorized binary carriers, we'll have to steganographically hide our traffic in fake voice calls. Crappy baud rate, but good enough for encrypted text. Augment with sneakernet and local hard-wired networks running under lawns and dorm room carpets.

Although in this grim future where all communication is monitored and censored, people like you and I will probably be up in the hills in the rebel camps, and open networking protocols might be low on our list of priorities.