In this thesis, we employ an open system perspective to explore the behaviour of matter fields coupled to dynamical gravity in thermal states, i.e. in the presence of a black hole, within the framework of semiclassical gravity. In recent times, the study of the gravitational path integral for low-dimensional spacetimes which are asymptotically AdS suggested a deep connection between black holes and the theory of quantum chaos, where different saddles of the path integral are interpreted as statistical moments of probabilistic observables. This thesis builds up on this idea approaching it from the point of view of open quantum systems, either studying the imprint of quantum chaos in systems coupled to dynamical gravity, or analyzing how such a probabilistic interpretation can be rephrased in terms of a non--unitary evolution. In the first part, we explore how quantum information can be retrieved from evaporating black holes, focusing on an ingenious yet simple setup called double holography. In the second part, we analyse black hole evaporation from the point of view of the Feynman--Vernon Influence Functional, where (dynamical) gravity is treated as an environment, that we integrate out in order to study the decoherence of black hole radiation. In the third part, we set up a conceptual framework which addresses semiclassical gravity in the context of stochastic signals. In particular, we interpret thermal correlation functions of simple operators of holographic systems as stochastic processes. This formally draws an analogy between semiclassical gravity and the theory of Brownian motion, where some universal features of the UV completion(s) of gravity are naturally embedded in the theory as probabilistic expectation values. We end this thesis with a proposal to perform quantum simulations of such holographic systems (specifically, the Sachdev-Ye-Kitaev model) on optical cavities, adding some concluding remarks and future directions.