This is a paid asset, but now you can download 100 Gradient Backgrounds for FREE, but please remember this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
100 Gradient Backgrounds v1.0
We introduce a versatile collection of 100 colorful gradients that are useful for you to create modern designs.
4K Resolution (3840x2160px)
Huge library of realistic gradients
Can be easily adjusted to fit your project
Extended license – create and use as many of these fonts as you’d like on your own personal projects as well as any commercial ones for clients.