Strongly coupled dark sectors offer natural UV-complete extensions to the Standard Model and interesting composite dark-matter candidates. If they are only weakly coupled to the Standard Model, they might be challenging to access experimentally. In this talk, I will present the possibility of testing these dark sectors via gravitational-wave signals from the first-order chiral or confinement phase transition. Due to the non-perturbative nature of the QCD-like sectors, we adapt lattice data to effective models from which we can compute the bubble nucleation in the early Universe. I will present results in a pure SU( N) Yang-Mills sector where we use the effective Polyakov loop model, as well as extensions including dark quarks in different representations employing the PNJL and the PLSM model.