Agricultural land is far from large population centers, so the value is relatively constrained. The real losers on an LVT is not those owning rural land, but the operators of a surface lot near a stadium, or people living in mansions in the innermost suburb ring.

They get taxed less, because instead of taxing their produce and income, their land is taxed, and agro land is very cheap. On a quick google, I can find a 140 acre alfalfa farm in Idaho for $1.4MM ($100k/acre), and a 0.07 acre empty residential dirt lot in NY for $4MM ($54MM/acre).

Land that is far away from developed land will tend to have lower land values, so farmland would not be so highly taxed under LVT. It's mostly land that benefits from being close to development that would be taxed higher.

Australia values every single lot of land for rates (aka council tax). So it is possible with some good stats nerds to figure it out.

But these values take into consideration zoning. So if you are ona residential block it is valued as such. But it would not be hard to figure out what it would be worth as high density. So the valuation problem is easily doable.

Also in Australia each state does it independently.

No, but they're also not punished if they do build