> Who decides which organizations are part of the fourth estate?
In the United States, given our Constitution enumerates certain freedoms for the press, there is a rich corpus of case law drawing this delineation. I am not sure if such a corpus exists in the EU, and am fairly certain it does not exist in every one of the EU's twenty-eight member states.
The First Amendment says "Congress shall make no law...abridging the freedom of speech, or of the press..." [1]. The comma is the delineation. In case law, the exploration of this delineation has produced definitions with precedent [2].
More practically, the linked-to article explores "whether the 'institutional press' is entitled to greater freedom from governmental regulations or restrictions than are non-press individuals, groups, or associations," concluding "the speech and press clauses may be analyzed under an umbrella 'expression' standard, with little, if any, hazard of missing significant doctrinal differences." (TL; DR There is a line, but it does not appear to matter much.)
In the United States, given our Constitution enumerates certain freedoms for the press, there is a rich corpus of case law drawing this delineation. I am not sure if such a corpus exists in the EU, and am fairly certain it does not exist in every one of the EU's twenty-eight member states.