There is LanguageTool, but it's a Java monstrosity. You can at least bind it to localhost and it's only slow on startup, but takes 300MB of RAM just sitting there, exposing a REST API.
They send all your texts to their servers for analysis. I don't find that acceptable from privacy standpoint, even if I'm just writing publicly visible comments.
if you're looking for spell and style checking I can recommend the hemingwayapp.com - doesn't catch everything but is pretty useful especially for non native English speakers
I can't read past this kind of error. It's a typo too far for an article that is asking me to take it seriously.
Proofreading is "proof" that the author has taken care of both their language and their ideas.