How did the people of Gondor know Aragorn was king? From their perspective, Aragorn is a ranger from a faraway land and a friend of Gandalf. They eventually learned that Gandalf supported his claim to the throne, but was did they know before that. This question asks how Faramir guessed/knew Aragorn was king. That means Faramir knew and he was well respected by the people of Gondor. Did they accept Faramir at his word? One person who may have known was Faramir's father, the Steward of Gondor, Denethor. He told Gandalf he wouldn’t bow to Aragorn, the “last of a ragged house long bereft of lordship and dignity.” If he did know, he certainly would not share that knowledge with the average Gondorian because that would make people think they should follow Aragorn and not Denethor.
Elrond knew of Aragorn's ancestry, but the people of Gondor have no reason to believe the word of a elven lord over their own steward.
This question shows why Aragorn was in the royal bloodline, but it does not mention if the commoners of Gondor knew.
Did the people of Gondor know Aragorn had a legitimate claim to the throne?