How can I represent different biomes on a Terrain object?

Hello! I am using the Unity Terrain object in my procedurally generated terrain. I want to have different biomes on my terrain (i.e desert, forest, ocean, etc.) I want to use different textures for the different biomes but if you see in the documentation for TerrainLayers at the bottom it says that having more than 4 Terrain Layers on a Terrain object will impact performance (for URP which I am using). My understanding is that a Terrain Layer is needed for each texture you want to use on the terrain. It seems odd to be limited to 4 textures, especially because I'd like each biome to have 4 textures on it's own at least!

My terrain is procedurally generated so I am breaking it into chunks. So I could restrict each chunk to be one biome. But there would be a really gross contrast between biomes, with no gradual shift between them.

Is there a better way to solve this problem?

If I do have to have harsh contrasts between biomes I was thinking maybe I could have the world consist of hexagons which could produce a cool looking result. But the issue with that is that the Terrain objects seem to need to be a square mesh (please tell me if I'm wrong).

I would love to use Unity's terrain system because of all of it's awesome features.