Comment by nunobrito

This is being solved with https://geogram.radio

Every phone/device is their own server, they connect with a web socket to the preferred station which is typically a server online serving as bridge.

There is no need to be always connected to a server, you can also connect locally on the WiFi, BLE or even USB-C cables (discovery is automatic).

From there are internal apps for sharing static websites, chat, blogs, files and so forth.