Hello
in the categories of the database, we have activated the publication on the forum.
but each member receives two notifications in the "unread content".
Would it be possible to have only in the "unread content" the article of the forum.

I have searched a lot but I did not find this option

If the user is following both areas, then they would indeed get 2 notifications. 1 for the article, and one for the forum post. The way to resolve this is simply not to follow one of them.