Keith Williams wrote:

Use a countersink drill bit to drill pilot holes. Also, there are
specially treated screws meant for HardiBacker with nice robertson
or square-drive heads (I can't tell the difference).

That is what I was trying. My driver just wasn't strong enough.
Concluded that with nails every six inches it wasn't going anyplace
anyway.

Just don't lay over linoleum. A neighbor did that. One came loose.
When trying to replace it they all came loose.