What is the Ruling of those who Deny the Sunnah Claiming Sufficiency with the Quran?

As already mentioned, they are not Quranis. Rather, they are liars and enemies of the Quran, because the Quran commands with the sunnah and obeying the Prophet ﷺ. Whosoever denies the sunnah has denied the Quran. Whosoever disobeys the Prophet ﷺ has disobeyed the Quran. They are not Quranis, rather they are against the Quran, and deviants. In fact, they are disbelievers by the consensus of the people of knowledge. Whosoever denies the sunnah, doesn't act upon it and claims that he will only act upon the Quran is a liar. He did not act upon the Quran. He is deviant, misguiding, and a disbeliever by the consensus of the people of knowledge. I have written a treatise about this that is published, I have named it as "Wujub al-amal bi as-sunnah" (The Obligation of acting upon the sunnah).