Could this also be "salt-free," such as you might see on a box in a grocery store?
It seems plausible, since gan cháin means “tax-free”. Im gan salann is “unsalted butter”.
Gan is unusual in that it generally (but not always) lenites B, C, G, M, and P, but it never lenites D, F, S, and T.
Would this be the same as, "except for salt."? Also, would it be far fetched to say "except without salt."?
“Except for salt” would be “ach amhain salann”.
Not sure about the other phrase...