"There are some open source websites that are trusted (e.g. https://arxiv.org"

Lol. Citing arxiv is even worse than citing wikipedia, and some reviewers will reject arxiv citations all together. It's full of junk 'science' by crackpots. Not just 'hey look I ran this regression on a public dataset' bad, but all-out 'I was abducted by aliens, and I made up an equation to show that they took me to Pluto' bad. Maybe it differs by field, I don't know - but suggesting arxiv is 'trusted' the same way Nature is 'trusted' is inane.