Description:
Despite having activated all the required options:
- Tools > Automatic Spell Checking
- Tools > Options... > Language Settings > Writing Aids > Check grammar as you type
I cannot get grammar to be checked.

Also, in the menu Tools, there is only an entry "Spelling... (F7)" whereas in the latest PDF documentation for Writer (only available for the earlier LO 6.0 version - see: https://documentation.libreoffice.org/en/english-documentation) it is supposed to be "Spelling and Grammar". However, when I click on Tools > Spelling... *while have the cursor in the middle of the document* the Spelling dialog opens with a message "Continue checking at the beginning of document?" under which one can see in the Checking dialog a "Check grammar" option unchecked (hinting at the fact that it should also be possible to check the grammar) but this option disappears once one closes the message.

On the other hand, in the interactive Help > LibreOffice Help (F1), it says: "Grammar checkers can be downloaded and installed as extensions. See the extensions web page.", with a link to https://extensions.libreoffice.org/extension-center?getCategories=Dictionary.

All this is quite confusing...
Is there a grammar checking function implemented in LO which relies on some grammar rules that would come as an addition in the same way as the spelling checker relies on added dictionaries? In which case all the above options that can be activated or inactivated make sens, but in the site extensions.libreoffice.org one can only find external services such as LanguageTool or Scriben relying on an online connection and data transfer.

What addition/extension did the grammar checking function of LO 6.0 rely on? And what happened to it? 

If the grammar checking only relies on external tools/services served as extensions, wouldn't it be clearer to rephrase those grammar-related options to be more explicit that they just enable/disable some grammar-services extensions (for example, replacing "Check grammar as you type" by "Enable grammar checking extension"), and to have those options greyed out when the user hasn't yet installed such extensions?

Steps to Reproduce:
General situation:
1. Open a document containing some grammar errors
2. Activate automatic spell checking (Tools > Automatic Spell Checking)
3. Activate grammar checking (Tools > Options... > Language Settings > Writing Aids > Check grammar as you type)
Regarding the 'hidden' "Check grammar" option:
1. Open a document
2. Required: place the cursor on a new line after some initial text.
3. Open the Spelling dialog (Tools > Spelling... (F7)

Actual Results:
No grammar checking is performed.
A "Check grammar" option is temporarily displayed in the Spelling dialog.


Expected Results:
One of the others:
- Grammar checking should be performed
- The options should explicitly refer to an extension to be installed and that is made enabled/disabled and the options should be greyed out 


Reproducible: Always


User Profile Reset: No



Additional Info:
[Information automatically included from LibreOffice]
Locale: en-US
Module: TextDocument
[Information guessed from browser]
OS: Linux (All)
OS is 64bit: yes
[LibreOffice install]
Version: 6.3.2.2
Build ID: 1:6.3.2-0ubuntu0.18.04.1~lo1
CPU threads: 8; OS: Linux 4.15; UI render: default; VCL: gtk3; 
Locale: en-US (fr_FR.UTF-8); UI-Language: en-US
Calc: threaded