  We study the fate of an impurity in an ultracold heteronuclear Bose mixture,
focusing on the experimentally relevant case of a $^{41}$K-$^{87}$Rb mixture,
with the impurity in a $^{41}$K hyperfine state. Our work provides a
comprehensive description of an impurity in a BEC mixture with contact
interactions across its phase diagram. We present results for the miscible and
immiscible regimes, as well as for the impurity in a self-bound quantum
droplet. Here, varying the interactions, we find novel, exotic states where the
impurity localizes either at the center or at the surface of the droplet.
