You can check languagetool. I believe there is a selfhost version as well, I even recall a cracked selfhost version. I am a premium subscriber of the original app at the moment, I understand it is not 100% privacy tight.
Repo for those interested: https://github.com/languagetool-org/languagetool
Couldn't find the cracked repo, if anyone had that please send it over!
LT works great for me, just as well spelling awful.
Grammarly and anything like it is literally just a linter for prose. A couple of years ago I set up Atom text editor with a few different libraries and packages, some of them cloned from Grammarly, to lint my writing.
You can configure it with any styleguide you need i.e. journalistic, professional, informal, etc etc. Do a little digging, it's all out there and lots of it is FOSS.
Privacy has become a very important issue in modern society, with companies and governments constantly abusing their power, more and more people are waking up to the importance of digital privacy.
In this community everyone is welcome to post links and discuss topics related to privacy.
[Matrix/Element]Dead
much thanks to @gary_host_laptop for the logo design :)