In a previous post where somebody asked about unity's default scripts he said:
"You can use engine defaults." So you can probably use starter content, but I'm not sure about the rest, I'm a bit curious as well :)
Viewing post in A few questions about acceptable resources.
I saw that, but it sounded like that was the equivalent to the blueprints in the templates in UE4. I understand using other peoples assets would be cheating (and against the spirit of a game jam) but I've never seen any jams on here specify if default materials or Substance Painter materials are allowed, and it would be sad to be disqualified.