You need to ensure that the following options are enabled:

* http://take.ms/11PFD

* http://take.ms/GlJoJ6

Yes, these options are already enabled but this only sets the post language.

The issue is that in the composer there is no more option to link the post to its translation

Hi there,
Can you try enabling this setting in the System - Language Filter plugin as well and see how it goes?
http://take.ms/dsxaQ

I'm not 100% sure but I think in the past the association was possible without that option on...
Nonetheless, there are 2 more points I would like to rise:
1. If you want to are only logged in in the administration the popup dialog box wants you to register in the frontend to be able to associate posts. That is in my opinion not logical...

2.A normal behavior would be that blog posts not translated in available site language display in the website main language. At the moment it does not.

IMPORTANT to me:
More over I need to activate that option ONLY for EB5...
and does this now break/impact the main SEO/SEF configuration/router/rules of my website ??
-- Question asked because I am using the Falang component where the associations and all SEO/SEF are entered in that component

I'm not 100% sure but I think in the past the association was possible without that option on...

I am really lost here. If you merely want to turn on the feature to pick a language for the post, http://take.ms/gC46l you do not need the "Language Filter" plugin.

If you want to enable post associations / language, http://take.ms/tLfBt hen you will need the plugin turned on.

1. If you want to are only logged in in the administration the popup dialog box wants you to register in the frontend to be able to associate posts. That is in my opinion not logical...

I have no idea what do you mean here.

2.A normal behavior would be that blog posts not translated in available site language display in the website main language. At the moment it does not.

I have no idea what do you mean here.