Hermetry takes MQTT 3.1.1 and HTTPS from devices, plus LoRaWAN through its own network server and polled SNMP and cameras. No MQTT-SN, no CoAP. So for anything non-IP the answer is a gateway on site that speaks the field side and talks MQTT up. Two ways I’ve done it:
Licensed gateway with Hermetry Edge. It reads Modbus RTU over RS-485 and Modbus TCP (depends on the model), dials out over TLS with its own certificate, buffers during outages, and each inverter appears as its own child device. You claim it with the code on its local Cloud page, nobody types credentials on site.
Your own gateway. A Pi or industrial PC reads the buses with pymodbus, reads the weather station’s serial radio and a 433 MHz receiver, and publishes for all of them on v1/gw/connect and v1/gw/telemetry:
{"INV-07": {"ts": 1793000000000, "values": {"p_ac_kw": 41.2, "e_day_kwh": 188.4}},
"WX-1": {"values": {"irradiance": 612, "t_amb": 9.8}}}Mark the device “This device is a gateway” when you add it, or every v1/gw message is refused and the session gets closed after three. If the inverters ever need commands, you send them to the child device and the gateway receives them on v1/gw/rpc. Your own gateway has to pass them on to the bus, a licensed one does that for you.
For a site that is probably unattended for weeks, I’d pay for the licensed box.