As much as they are for us. Dark matter is matter that only reacts to us via gravity, so the effect of a black hole which also only acts via gravity^1 is the sa

As much as they are for us. Dark matter is matter that only reacts to us via gravity, so the effect of a black hole which also only acts via gravity^1 is the same for them as for us. ^1 I am ignoring charged black holes here, because astronomical black holes should be basically uncharged and my intuition is, that if there is some kind of dark charge, then the black hole could also be charged under that force.