So, I was wondering if, hypothetically, you could make a dynamic material shader (such as snow build up on another material) work with a landscape material? Basically have snow accumulate on grass that’s painted on the landscape, etc.
Yes you can dynamically change a material on your landscape -> parameters 
(should work the same with a landscape material)
e.g in this video you can see how you can change the roughness value of your landscape: ?v=D_6VKS2nNMU Should also work with all other params.
Yeah, I know how to make a dynamic shader 
The reason I asked was because I made a dynamic snow shader that I wanted to apply to the terrain. I just didn’t know if it was applicable to terrain materials.