This worked for me as well but there’s more to it.
After following your instructions, my landscape was using the correct physical material, but when I changed the physical material again, it didn’t update. I realised that you just need to change the “Simple Collision Mip Level” to anything other than what it was. Once that value updates, the landscape will update to the new physical material.
So in other words:
- Assign your landscape a physical material.
- Go to your landscape collision settings.
- Change “Simple Collision Mip Level” to a new value to “lock in” your physical material.