Problem has been checked with two different 6.3.X versions and only appears since 6.3 versions (a regression) (no problem in any of 6.2.X version)

On Win10 (ver 1709) with LO 6.3.2.2 x64, if I type:
"Les éléments sont les suivants"
then I type ":", a non break space appears.

Then 2 possibilities:
1) if I type a space
=> the non break space stays so I've got:
"Les éléments sont les suivants : " (only the space before colon is a non break space).

2) if I type something else than a space (eg: just a "b")
=> the non break space disappears and I've got:
"Les éléments sont les suivants:b"

I had read this behaviour was expected. (I must recognize I should search references for this).

You're right : this behaviour conforms to the expected (W10 environment).
But it's note the case in Linux (kubuntu) environments (18.10 and 19.04) on both LO V6.3.1 and V6.3.2) : no unbreakable space appears whatever a space is entered or not.
Thanks a lot for your investigations !
I could help if appropriate.

(In reply to Jean-Philippe LEBRAT from comment #3)
> You're right : this behaviour conforms to the expected (W10 environment).
> But it's note the case in Linux (kubuntu) environments (18.10 and 19.04) on
> both LO V6.3.1 and V6.3.2) : no unbreakable space appears whatever a space
> is entered or not.
> ...

On pc Debian testing x86-64 updated today with LO Debian package 6.3.2.2, I got the same behaviour as the one I had on Win10.
apt-cache show libreoffice
Package: libreoffice
Version: 1:6.3.2-1

Quite weird you don't have the same behaviour on Kubuntu which derives from Debian.

Do you confirm you install LO from Kubuntu repository and not by downloading from a website (even official one)?

Also, could you rename your LO directory profile (see https://wiki.documentfoundation.org/UserProfile#GNU.2FLinux) and give a new try?
I don't expect much but it's just to be sure it's not related to profile.

You're right : from available Kubuntu (19.04), I only access to the 6.2.X LO versions, so I installed the 6.3.X version through LO WebSite downloading (as I used for many years...).
So OK for closing the bug (I should install through adding the ppa:libreoffice/libreoffice-6-3 repository).
Thanks !

Concerning Official LO website, Linux packages are more for repository maintainers of the different Linux distribs.
For example, they must manage dependencies, the upgrade between former and new version, etc.

Let's put this one to WFM then.

Of course, don't hesitate to reopen this tracker if you reproduce this with LO 6.3.2 from Kubuntu repository on a clean env.

For information : unfortunately the bug remains in case of a clean installation (from ppa, especially for LO 6.3.X versions).

More precisely, I uninstall LO (all packages an dependencies), then (under kubuntu 19.04) :

sudo add-apt-repository ppa:libreoffice/ppa
sudo apt-get update
sudo apt-get install -y libreoffice
sudo apt-get install -y libreoffice-kde5
sudo apt-get install -y libreoffice-l10n-fr

Then test.
Then I add the "Grammalect" extension package.
Then Test.

Before and after the Grammalect extension package, no unbreakable space is provided (neither from manual or automatic space input before ":", "?", "!"), and after installing the Grammalect extension, mistakes are underlined under spaces which are not unbreakable (before ":", "?" and "!".

Sorry...

I will reopen the bug if confirmed under Kubuntu 19.10 or 20.04 native installation.

(In reply to Jean-Philippe LEBRAT from comment #7)
> ...
> Before and after the Grammalect extension package, no unbreakable space is
> provided (neither from manual or automatic space input before ":", "?",
> "!"), and after installing the Grammalect extension, mistakes are underlined
> under spaces which are not unbreakable (before ":", "?" and "!".

Did you rename LO directory profile to force LO to recreate one and so to start with a pristine LO profile?

> Sorry...
> 
> I will reopen the bug if confirmed under Kubuntu 19.10 or 20.04 native
> installation.
Don't be sorry, no problem! :-)