Does anyone know if there will be an equivalent of the Game Jam Start Kit for Godot instead of just the Unity one?  Or,  is there a reliable way that the .unitypackage files can be ported into Godot?

This will be my first Gam Jam and I've been learning Godot through the GameDev.tv course (Thanks, Bram!), and I'd love to be able to use the resources y'all are providing!

Afaik they won't be, however there are plenty of sites to get freebies. 

Kenny Assets is a pretty big name one.

Here on Itch there are plenty of CC options as well.

opengameart.org is a fantastic source for all sorts of stuff as well (a lot is CC0)