As-Salaam alaikum,
As you are aware, the Sunnah refers to the commands, prohibitions, actions and tacit approvals of the Prophet Muhammad, Sallallahu alaihi Wasallam. The whole of the Sunnah falls under the Command of Allah Ta'ala in His Book where He says:--

"Whatsoever the Messenger gives you [then] take it and whatsoever
he prohibits you from, [then] refrain from it." (al-Hashar- 59:7)


And in the Hadith, the Prophet, alaihis-Salaat Was-Salaam, said:--

"Let me not see one of you, reclining on his couch, when he hears something
regarding what I have commanded or forbidden saying: 'We do not know. What
we found in Allah's Book e have followed' "
[Abu Dawud].

This is a good reminder against today's attitude with which some Muslims, unfortunately, discard the Sunnah of our Prophet, Sallallahu alaihi Wasallam. Allah, Subhanahu Wa Ta'ala, repeatedly links obedience of Allah to obedience of His Messenger. Allah says: "And whosoever obeys the Messenger, thereby obeys Allah". (4:80) This Ayat, taken together with Ayat 7 of Surat Hashar quoted above, condemn having a 'Qur'an only' approach.

To divorce the Sunnah from Islam is to render Islam ineffective.... for example, the Qur'an directs us to pray, but without the Sunnah, how would we know how to pray? or how would we know how to calculate and give/pay Zakkat?... one of the 5 pillars upon which Islam is built... and many other issues. So, Beware!! Keep to the Sunnah of the Messenger of Allah, Sallallahu alaihi Wasallam..