Would also be neat if there was a way to build a LoRA proxy to extend the range. I might give this a try with my meshtastic devices.
It's an Arduino library for mesh networking, that works over BLE and UDP, but it can also link to MQTT.
An MQTT node routes the packets it sees to the appropriate topics, and subscribes to topics for all the channels local nodes want, so you should be able to talk to anyone anywhere via the gateway.
The packet destination addresses are rolling codes, so you can't tell if someone's online just by watching their channel, at least not for more than an hour.
And there's a web app that talks directly to the public MQTT broker, and it can do chat and sensor data.
All payloads are Messagepack to make it easy to add new data types, and all packets are encrypted, authenticated, and timestamped to provide a bit of replay protection.
Everything is purely symmetric crypto, trust is left to a higher layer or something out of band, so you there's no handshakes or connection state management overhead, aside from one announce packet per hour to make the MQTT gateways work.
No LoRa, but the transports are modular and pluggable so you can easily add them. I just only have one LoRa Arduino node here so I haven't bothered writing a driver.
I'm also working on a Python port for easy pip-installable bots and home automation stuff.
I wonder what other transports you could do, like 38khz IR through a telescope?