I keep using LibreOffice for just the spell & grammar check, earlier it was MS Word.
Is there an offline version for English language that is multi-platform?
Basically an app like Windows Notepad with spell & grammar check.
Software Recommendations Stack Exchange is a question and answer site for people seeking specific software recommendations. It only takes a minute to sign up.Sign up to join this community
Notes on the Mac has spelling and grammar checking. Most Mac apps have this. Goto the edit menu and there is a spelling and Grammar selection. You can turn these on by selecting options you want. I don't know how well these work. Since this seems to be a system wide option it works with Textedit too.
You can also get a free account with Grammarly. It runs in background but monitors everything you type.
Use Grammarly as an add-on in your favorite text editor. Its recommendation engine is intelligent, updated, and linguistically good. It works on browsers too.
Grammarly website - https://www.grammarly.com/
You will get add-ons for various editors and browsers, like, MS Word and Chrome, on this website itself.