This is the 13923rd most frequent Polish word.
popularnego
"Popularnego" means "popular" or "commonly known."
Here, 'popularnego' is used to describe an author who is widely known and liked.
Czytałem książkę popularnego autora.
I was reading a book by a popular author.
In this example, 'popularnego' modifies 'rodzaju', indicating a category or type that is well-liked or common.
Restauracja znajduje się w popularnego rodzaju budynku.
The restaurant is in a type of building that is popular.
Here, 'popularnego' is describing 'tematu', showing that the subject of the competition is widely appreciated or talked about.