The Scrum Guide is the definitive guide of what artifacts are in Scrum: The Product Backlog, Sprint Backlog and Increment.
It would certainly be possible to make a case for the "Definition of Done" or "Sprint Goal" being artifacts, but that is not stated explicitly in the Scrum Guide.
As Scrum is a framework it leaves a lot of room for adaption. Hence you may see lots of different views and possibly even contradictions around what constitutes a Scrum artifact.
It is also worth noting that the Scrum Guide itself is not set in stone. It is reviewed frequently and there have been many updates over the years.