If you’ve got the dough and the space, go for a whole-house water softener paired with a simple RO system under your kitchen sink. You get soft water everywhere (showers, laundry, dishes) and pure drinking water from the tap. It’s the luxury SUV of setups.
Top 11 Water Filters for Tackling Hard Water - Water Filter Stuff
On a budget? Grab an APEC WFS-1000 countertop filter. It’s cheap, it uses ion exchange, and it’s actually tested for hard water. I’ve used one. My coffee tastes less like a geology experiment now. True story.