This is a recent propaganda that Wahhabis are flagging against Shias. There is no Sunni chain of narration which lists all the transmitters followed by whole Qur’an as is now. If the say they have the chain of narration of Qur’an that should look like Bukhari and Muslim’s Ahadith which follow the actual words of Hadith at the end.
If they have any Riwayat of that kind ask them to produce.
In fact I asked that Salafi to forward me any Sunni chain of narration for Qur’an itself (not the Qirat) and he was dumbfounded.
Qur’an’s authenticity is beyond these nonsense arguments.
Chain of narration Is required for the traditions not for Koran. Quran is Mutawwatir, and Mutawaatir doesn’t require any specific kind of narration.
Furthermore we have our holy imams ,the successors of prophet Muhammad (saww)who continued to exist all the way from the demise of the messenger of Allah in 11 AH all the way till 260 AH, who always recited this Koran referred to this Koran and asked all the people to read write memorize the Quran as is now. This is the greatest authenticity and validity of the Quran for both Sunni and Shia Muslims.