Spell check is fine but grammar check doesn’t work.
Click on Tools, Options, Language Settings Writing Aids. Check to make sure Lightproof grammar checker (English) in the top box is checked, then make sure Check Grammar as You Type is checked in the box at the bottom called Options.
The click on English Sentence Checking back under Language Settings and check what you want to be checked under Grammar checking.
I know this is a couple of years old but I just came across this because I’m trying to enable grammar checking on LibreOffice and my copy doesn’t even HAVE the “Lightproof grammar checker (English)” option in the exact place you mention.
I am on Ubuntu 20.10. The solution is to install the “libreoffice-lightproof-en” package (I found this simply by browsing apt packages that had “lightproof” in the name). I’m not sure why this package is not installed by default on my distro, but after installing it, the option you describe becomes available.
Unfortunately, I can’t tell whether the grammar check works or not, because it does not complain about “The quick brown fox jump over the lazy dog”, “I took pill in Ibiza”, and other grammatically-questionable sentences. I discovered that most of the options are off by default, so I enabled them, but it didn’t make a difference. I’m not sure what Lightproof actually checks…
I seem to recall having better luck with LanguageTool extension.
This is a common question and lots of ask from users. This has been explained with screenshot to enable grammar check automatically in LibreOffice Writer:
No. This did not work then and it still does not work today. Any other ideas?
Have you updated to the current version of Libreoffice?
I have version 24.2.4.2 (x8664) and mine works.