Lionel Lingelser is [Spoiler (click to open)]King Louis XV.
He's 34. Here is his Facebook (he is listed as a "Comedian), his IMDB, and AlloCiné.
"A graduate of the National Conservatory of Dramatic Arts in Paris, Lingelser stars in Jean Emmanuel Godart’s forthcoming feature Big House with Gérard Depardieu. He is set to recur in the new [Outlander] season that will is expected to return in the spring."
Thanks to summerstar882 and the source.