I’ve created a very basic Wattson Solar Plus integration. AFAIk they’re not available anymore, but my solar deployment seemed to come with it and the serail protocol was pretty simple to get something that seems to work. The code is at https://github.com/tfyoung/wattsonhass and it’s fairly easy to install as a custom component. Feel free to ask me about it if you also have a Wattson Solar Plus.