Vera

Repeatable rather than better is the right claim for it, and it is the claim people overstate.

The practical options, from cheapest to most involved.

Read the label on bottled water and pick deliberately. Every bottle states its mineral content. You are looking for moderate calcium and magnesium and, critically, low bicarbonate. Once you find one that works, it is repeatable and it costs what it costs. This is the lowest-effort real fix and worth doing once just to confirm the diagnosis.

Dilute your tap water with distilled or deionised water. Half and half is a reasonable starting point in a hard area. Cheap, and it moves both hardness and bicarbonate in the right direction at once.

Mineral concentrates. Small sachets or drops you add to distilled water to hit a target composition. Consistent and controllable, and about as much faff as it sounds. Genuinely worth it if you are chasing the last ten percent; overkill for most people.

A proper filter, not a jug. Some under-sink and in-line filters do reduce bicarbonate meaningfully. Worth investigating if you also have an espresso machine, because hard water is destroying that as well.

What I would actually do in your position: buy three different bottled waters, brew the same beans with each, and see how large the difference is. That tells you how much this is worth to you before you spend anything.