People talk about Jon Snow having claim but the only person who could validate that claim was dead. They obviously respect his status in the north which is why he could have gone on to rule Winterfell under different circumstance.
No. The person I'm talking about is Gendry.
The fact of the matter is Robert Baratheon had only one real son. That son was Gendry. That claim was validated through Daenerys herself through royal decree and multiple parties (including Stannis and Seaworth) also validated him.
Robert Baratheon sat on the Iron Throne. He legitimately succeeded the House of Targaryen. The only legitimate heir to that house is now dead having been killed by Jon Snow. That means the only person who had true claim to the throne was Gendry.
He may have settled for a title as king of Storm's End but he's ultimately the true king of the (now six) Kingdoms.