Well, since I come from a place where they make and export LOTS of butters of different types all over the world. I probably can comment here.

I must say that I think putting the butter in the Fridge is the only way to go.

The fridges all made here have a special "butter conditioner" little box inside the fridge (up near the top where there is less cold air) where you can put your bar of butter in the (supplied) plastic tray with clear plastic cover and it keeps it warmer than the rest of the fridge (some sort of little heater thingy in there), so that it spreads better on your toast etc.

That yuckky "yellow" rind/oxidised bit you get on the outside of the butter is probably for sure, more harmful than the "fresh" butter further inside the bar, so leaving out your butter is a non-starter as it gets this nice rancid rind.
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Still if you live in a cold enough place then "leaving it out' might be the best way forward.

IMHO - the fridge is probably the best place for butter.

They also make here a special butter (called "spreadable butter") that has extra water mixed into it once the butter is made so that it can be spread straight from the fridge on your bread and toast.

The extra water content changes the flavour none but helps make it very easy to spread and is really the *only* option if your fridge has no butter conditioner.
[it makes it about have about the same spreadability factor as that horrid stuff called margarine - but with none of that "chemical" aftertaste :-) ].

The Spreadable Butter product was developed for the UK/Europe where fridges with butter conditioner don't exist.

Don't know if the product is available in the US - given the surfeit of Dairy products already sold in the US, I doubt it, or it would be very hard to find.