This is a fictional representation of a real life person.
Stéphane is a real life Swiss figure skater and choreographer who plays himself commenting on the Barcelona Grand Prix Final in Yuri!!! On Icein Episode 12. He is known for his spins (and more specifically, his ability to spin both clockwise and counter-wise). But as he is 31 in reality, he is retired in the anime.
In the show, Stéphane narrates in French, even when talking to other commentators, who reply to him in Japanese. It is not certain what the canon language Stéphane speaks in is. In the English dub, his voice was replaced with another voice actor's.