A true water softening system will require salt. There are alternatives, such as an anti-scale system, which crystallizes the hard minerals. They are still in the water, but don't stick to things as much.

Yeah, where I grew up, a water softener was pretty much a requirement. Usually people put them downstream of the hot water heater so only hot water got softened (tub beauty more important than toilet tank beauty), but there was no work-around to avoid using one completely. I don't remember it being a big hassle to add salt, but maybe that's just because I was a kid and didn't have to do it. (Feels on the same scale as changing furnace air filters -- a couple times per year. I'm sure those living with them now will correct my memory.) Who should do it will be a local issue; probably some plumbing company.

Usually people put them upstream of the hot water