Billboard Renderer only works with Speed Tree Billboard shader. Why?

Hello, I am working on an environment and I am modeling my own trees using Treeit. I need to setup billboards for these trees.(for performance) By following other threads, I managed to render and create billboard assets however billboard assets only work with SpeedTree shaders.(which is not specified in the manual, and is not what I want.) Is there a way to work these assets with other shaders? I am using URP. Thanks.