"...what line a non-taxable cash distribution to a beneficiary should be reported on"
There actually is no line because if the only distributions were nontaxable, cash distributions and the trust otherwise had no income, there would be no 1041 filing requirement.
Regardless, when filing a 1041, the distribution would wind up on Line 10 of Schedule B. The distribution would not, however, appear on the K-1.
In TurboTax Business, you would include the nontaxable distribution amount in the Distributions section (Distribution amounts) in the Other Amount (Second Tier) box (see screenshot).
