I’ve installed a couple of EG4 6500EX-48 solar inverters/chargers (made by Axpert/Voltronic) … and successfully connected them to SolarAssistant. In SolarAssistant, I’ve activated MQTT …
https://community.openhab.org/t/voltronic-inverters-binding-4-3-6-0/ is an openHAB binding, which reads data directly from the inverter. This way you can skip SolarAssistand and MQTT. It is tested only with direct USB cable connection between the inverter and openHAB, requires separate cable for each inverter (no support for parallel mode), requires replacing the nrjavaserial-5.2.1.OH1.jar file from the openHAB distribution and is tested with only one model. But it integrates nicely with openHAB and has low overhead, so data can be polled from the inverter very frequently (I do it every 1.6 seconds).
Out of curiosity, how ofter does SolarAssistant fetch data from the inverter?