GD20 can be found @ https://cosmic-sorcery-society.itch.io/gd20.
Templates
One-Page Zine Template - 8-page micro zine using 1 sheet of printer paper.
Template Pack: Trifolds - classic trifold pamphlet using 1 sheet of printer paper.
24XX SRD - If you're stuck on ideas on how to organize your one-page setting or what to include, this is a fantastic resource. GD20 was built on a modified version of this template.
WTF Pamphlet RPG Template (affinity publisher)
Standardcat Template Pack - An Affinity Publisher template for roleplaying and other books
Assets
Human Creations for Creative Humans - A curated list of human made free, PWYW, and paid assets for TTRPGs.
Game Icons and Flat Icon - Free icon graphics.
Unsplash and Pexels - Free stock photo