How to count based on the results of a GROUPBY?

I have a table of donors and their gifts. Many people gave more than once, but some didn't giveat all. So I can do a

=GROUPBY(list[donor], list[gift], SUM) 

and I can see that a few of the donors have 0 so they didn't give. I want to get a count of these people, and i can't figure out a way to do that. I tried wrapping it in a COUNTIFS but that just produces an array of 0s.

Basically I want the equivalent of SQL's HAVING function. Any thoughts?

EDIT: got it figured out! I just need to repeat the whole choosecols bit in the filter:

=COUNT( FILTER( CHOOSECOLS( GROUPBY( FY24Trustees[TrusteeName], FY24Trustees[GiftAmount], SUM ), 2 ), CHOOSECOLS( GROUPBY( FY24Trustees[TrusteeName], FY24Trustees[GiftAmount], SUM ), 2 ) = 0 ) )