One of the paper's authors here.

GoTenna is definitely similar in its use-case and appearance. The problem with GoTenna is similar to FireChat for offline communication: they are closed ecosystems, single purpose and cannot easily be changed to fit specific needs. If you need something consumer-grade, ready to use: go for GoTenna (or Sonnet or maybe even a Garmin InReach or Spot X).

We propose different proof of concepts in the paper that are nowhere near the product quality of commercial solutions. Also, the chat application is single-hop and does not yet use a DTN underlay, at least not in the published version.

But all code is open and can easily be extended. Even better, the rf95modem firmware is designed to be used as-is. Once loaded on a LoRa board anyone can implement anything over device-to-device LoRa, be it a msg app, local news broadcast, IoT monitoring. This works via AT commands over USB serial interface, local esp32 WiFi or BLE.

That's great! A known shortcoming of Gotenna is that it assumes civilization (play/app store, Internet access) in order to set it the device, which isn't totally reassuring to go off into the wilderness with (its primary use case).