Don’t wanna brake you just a hint upfront. Almost any inverter can do modbus and unless you have specific needs such as to implement some extra control logic it is often sufficient to parametrize a modbus binding thing and set of items.
That’s already a huge improvement over MQTT as we don’t have to fiddle with synchronizing config in two places (OH and MQTT broker) it’s only OH config then.
I am using an inverter in an VPN connected subnet (192.168.177.xx).
The server (Synology NAS with Grott + Openhab) is located in a different subnet (192.168.178.xx)
Will this method (Grott Service on Synology NAS (in Docker?)) work as specified?
You create the bridge thing manually. Once the bridge thing is created, it will show status unknown. But once the grott application sends data to it, two things will happen 1) the bridge status will change to online, and 2) an inverter thing coresponding to the received data will appear in the Inbox (where you can then instantiate it).
I agree to Sebastian, there is no option to add things to the binding installed from marketplace.
If I am using the linked .jar file openhab is not recognizing the binding.
“The marketplace bundle was successfully installed but doesn’t start: Could not resolve module: org.openhab.binding.growatt 
Unresolved requirement: Import-Package: javax.measure; version=”[2.2.0,3.0.0)“”
The solution might be here (common issue with 4.1 versus 4.0.x)