According to Gabonese news outlet isport.ga, the 23-year-old does not want to return to parent club Sunderland - having spent the second half of the season on loan with Watford - while a switch to Lyon has also been discredited.
A source is quoted as saying: "One thing is certain, Didier will not play next season in Sunderland, a club relegated to the third division. Currently there are three serious paths. Cardiff City, which has just been promoted to the Premier League, and where Bruno Ecuele Manga plays, is one of the most serious paths.
"The agents of the players are activated. But there is also Lyon who are interested in the profile of the player. Unfortunately Didier Ndong does not wish to return to France."
Ndong, capped 18 times by Gabon, did not make a single appearance for Watford in his four months at Vicarage Road.