I have a Solis inverter [0], while it has WiFi built in, and we have the data logging dongle, it doesn't need to be connected to the internet to function, and you can configure the dongle to talk to MQTT locally (but I haven't done this).

It doesn't need to be connected to the internet during configuration either, we set it up and got it going before connecting the data logger to it.

That said, I do use their portal to see my generation and consumption. It's pretty handy. But I also do scrape their data and store it locally as well.

[0] https://www.ginlong.com/rhi_3pinverter1/29118.html

* I'm not affiliated with them in any way, it's just the one we have