NY wrote

I'm about to try brewing beer from a kit. Our tapwater is fairly hard,
but the house has a water softener (*) for one of the kitchen taps.

Is it better to use hard water, as it is supplied,
or to use water from the softener?

Hard is fine.

I can't detect any difference in taste of
water from the normal or softened tap.

The taste will be swamped by the taste of the beer.

(*) One of those inline cylindrical ones that is fitted with compression
fittings into a branch of copper piping off the rising main.