Some people install softeners outside. Yes, outside. Right by the hose bib. It looks like a weird silver robot guarding your yard.
Outdoor units need serious weather protection. Direct sunlight is a silent killer. UV rays degrade the plastic. Rain gets in. Bugs make nests. It’s a risky move.
But if you live in a temperate climate (hello, California!), it can work. Just buy a weatherproof cover. And maybe name your robot. I call mine “Bubbles.”