Frank Herbert"s DUNE

In the DUNE universe, what happened to Earth?
Destroyed during the Butlerian Jihad?

I don’t think we’re ever told. I recently finished reading Dune: House Atreides and Dune: House Harkonnen, have yet to get the Dune: House Corrino. The fate of Earth is not mentioned, though a few details about specific incidents during the Butlerian Jihad do come out.

My impression was always that it had been nuked to pieces ages and ages before the Butlers.

Not canonical, I think, but here you go:

That’s the last mention of Terra/Earth at all. So it’s still up in the air. But what we know from this timeline (from the Dune Encyclopedia) is that earth was hit by a planetoid, presumably decimating the ecosystem/population, the surviving treasures were removed, and the planet was then rehabilitated and left undeveloped under Imperial edict.