Chrome Extension with a private LanguageTool server

I am wondering if it would be possible to reroute the LanugageTool Chrome extension to use a private server. Is it possible? If so, what has to be done to make it work?

Yes, just set your server in the settings under “Experimental settings”:

How to run the server is documented here: LanguageTool embedded HTTP Server | dev.languagetool.org

Excellent. Thank you.

Does it mean, that if I install the open-source LanguageTool server on my PC and reroute the Chrome extension to it, that I will be able to use all Premium features free of charge? Please clarify.

No, the premium version is not available for local installation (except there’s an on-premise version, but that’s only available for Enterprise customers).