Who was the first person to conjecture that our Sun is just another star?
Relatedly, what was the first evidence that this was true?
As quoted from this article:
Many people's work was needed to prove that the Sun is a star. The first person we know of to suggest that the Sun is a star up close (or, conversely, that stars are Suns far away) was Anaxagoras, around 450 BC. It was again suggested by Aristarchus of Samos, but this idea did not catch on. About 1800 years later, around AD 1590, Giordano Bruno suggested the same thing, and was burnt at the stake for it. Through the work of Galileo, Kepler, and Copernicus during the 16th and 17th centuries the nature of the solar system and the Sun's place in it became clear, and finally in the 19th century the distances to stars and other things about them could be measured by various people. Only then was it proved that the Sun is a star.
So the first conjecture would date back to the Greeks, however there was much controversy surrounding the idea because to it's resemblance of the gods. It seems that it is a relatively recent fact.