Associating easy, as it needs work something similar to:

https://www.mediawiki.org/wiki/Manual:Messages_API#Notes_about_gender.2C_grammar.2C_plural

Thanks @Purodha, good catch.

Maybe it is better to simplify the string altogether:

A [[$2|new issue]] of "$1" is available.

(Don't take the syntax literally, what it means is that "new issue" would link to the new issue.)

I have installed Newsletter extension and created a newsletter. Can anyone tell me how to reproduce the bug?

It depends on the interface language you are using. Some languages need to be aware of the grammatical gender of $1.

Could you explain how to get the the Newsletter-notification-title page and in which language can I generate it?

I have no idea how you get there.

I am only a translator. As such, I found the message at https://translatewiki.net/wiki/MediaWiki:Newsletter-notification-title or https://translatewiki.net/wiki/MediaWiki:Newsletter-notification-title/en , respectively.

You cannot generate it in languages - or I misunderstand what you are asking for.
It should - where ever that is - appear in the language you selected as you interface language, or by default in the wiki language, when you encounter it. You can find all existing translations at https://translatewiki.net/w/i.php?title=Special:Translations&message=MediaWiki%3ANewsletter-notification-title

As for the Colognian Ripuarian translation, I deviated from the original message a bit which allowed to get along without the need to know the grammatical properties of $1 by using $1 as an attribute to the word "Rondschrihve" which is an approximation of "newsletter". But still, depending on its grammatical properties, this may not be good. I believe that it is like the best we can have, unless we find a way to convey things such as the grammatical gender, etc., of $1.

In T126731#2069154, @Abhinand wrote:

Could you explain how to get the the Newsletter-notification-title page and in which language can I generate it?

In any language that is translated and has a grammar construct like the one covered in this task. To "get to the page" you will have to install the extension and play with it.

@Aklapper I have cloned the extension but I am unable to generate the bugged page in my host to test. Need help :)

@Abhinand: What exactly have you tried so far to create/see the "page"? (Please also see https://www.mediawiki.org/wiki/How_to_become_a_MediaWiki_hacker#Feedback.2C_questions_and_support about expectations and good questions.) I'm not even sure you need to (though testing is always good). See https://www.mediawiki.org/wiki/Manual:Messages_API#Notes_about_gender.2C_grammar.2C_plural for what is needed.

I also think that actually running the extension may be not necessary. I would rather suggest that rewording the message to something like "... an new issue of the newsletter the name/title of which is '$1' ..." would do. It might even suffice to mention in the /qqq message documentation that translating the message like his would be alright - if it is so, of course.

Change 273750 had a related patch set uploaded (by Abhinand):
[[MediaWiki:Newsletter-notification-title]] is reworded

https://gerrit.wikimedia.org/r/273750

Change 273750 merged by jenkins-bot:
Reword [[MediaWiki:Newsletter-notification-title]] to fix grammar issues

https://gerrit.wikimedia.org/r/273750

all patchsets on this task seems merged. Should we still keep this open ?