Bran is The Last Hero.
Jon is the PTWP. Rhaegar got it right. It was his son, just not the one he thought it was.
Also: The Kingsguard at the Tower of Joy would NEVER fight anyone to the death over anyone’s bastard. Not even Rhaegar’s.
If Jon was a bastard, Arthur Dayne and the other KG (1 in the show, 2 more in the books), at Rhaegar’s depature to join the war, would have taken Lyanna to Starfall, and cared for her and her pregnancy there, where it’s safe, and there’s a Maester, and where no one cares that there’s a Targaryen bastard.
There’s only one reason for the KG to fight anyone to the death: to guard the rightful King.
Jon’s legit, because Lyanna & Rhaegar married, because plural marriage are what Targaryen’s have been doing for centuries.
And if Rhaegar ordered them to stay at the ToJ, they would have taken Ned to his sister, assisted him in packing up her and the baby, and shipping them back to the North.
Jon is the rightful heir to the Iron Throne. (Not that he will care, or that it’s important in any way in the light of the Army Of The Dead coming to end Humanity itself.)
Jon = The Prince That Was Promised.
Dany + Dragons = Lightbringer
Jon + Dany = Azor Ahai Reborn.
Jon will wield his Lightbringer, and “the darkness will flee before him.”