I went down the rabbit hole about Pytheas.
Seems that his almost contemporaries (300 BC) called him a fraud. Scorned as a common person. He was perhaps driven by money to a degree (to find the tin and amber sources), but was mostly a scientific explorer. He had some device to measure latitude, and his measurements confirm where he said he was. (North-south anyway). So it might have been Iceland (which he called Thule), or it was Norway. He even got to the “congealed sea” (frozen/slush).
Pliney and others later on also referenced his work, and based on later discoveries figured Pytheas as reliable.
Yeah, he went where he said he did. His critics (living and dead) remind me of people who claim that Marco Polo never went to China because — like Jacob of Ancona and others who went overland to China and back during the Middle Ages — he didn’t mention the not-so-great Great Wall, which by that time had crumbled into ruin, particularly in the area used by the Silk Road.