We prove that there exists a C ⁎ -diagonal with Cantor spectrum in the Cuntz algebra O k for 2 ≤ k < ∞ . Our method generalises to an uncountable family of UCT Kirchberg algebras with distinct K-theory. Moreover, we construct principal étale groupoid models for these Cuntz algebras and UCT Kirchberg algebras.
Evington et al. (Sun,) studied this question.