It’s right in front of your eyes. Paul refers to oral teaching he did or intends to do. So does Luke. So does John. So does Jude. So does Peter. ALL refer to oral teaching from the apostles or those sent by them as authoritative and binding. If you dismiss apostolic teaching just because it’s unwritten, you dismiss the written scripture also. They are indissolubly linked, a single body of teaching.
I asked what teaching it was that they passed on, how do we know it’s theirs, and how do we know that it was faithfully passed on.
Your response answered none of those questions.