This is a solution thread for all of you who are struggling with this like I did!
I made a video walkthrough and provided the liquid code to show how to display a flat discount percentage across all products/variants, using an automatic discount (for the cart) and some small code changes for the products pages and collections, grids, etc. (liquid templates provided in the video description).
Enjoy! I’ll make some more videos as I implement some more logic, like only applying to specific collections, etc.
https://www.youtube.com/watch?v=is0KxqXUYns