From the US Constitution: Section 3: Presidential responsibilities

"He shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such Measures as he shall judge necessary and expedient; …."

Summary: The President is constitutionally required to tell Congress the "state of the union". He does not have to do it in person. It could be a phone call, a video, a letter, or a speech in person. There is no requirement to tell the public, just Congress.

From https://psmag.com/news/can-pelosi-stop-trump-from-entering-congress:

The President can walk into the Capital building, uninvited.

The President can walk into the House of Representatives, uninvited.

Due to House Parliamentary Procedures, the President can not give a speech from the podium without the House (Pelosi) permission.

"Of course, parliamentary procedures might not be enough to stop the president from speaking, even if Pelosi bangs her gavel and tells him to stop. This would lead us into uncharted territory. Members who speak out of order open themselves up to "censure or such other punishment as the House may consider proper," according to existing rules. But for a non-member speaking out of order, it's hard to tell what exactly could happen. For protesters interrupting House business, the congressional sergeants at arms and other officers will remove the offending parties. Whether or not this would happen for a sitting president is a question that has not yet been answered in U.S. history."