He is not required to. Also for the second time John Roberts rushed the oath. Several presidents chose not to. Not saying Trump chose not to, but it’s not a point of contention
Article VI Supreme Law
Clause 3 Oaths of Office
The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.
https://constitution.congress.gov/browse/article-6/clause-3/