A Scrum Master and a Release Train Engineer are quite similar. In fact, in SAFe, it might be referred to as a Chief Scrum Master who leads the Scrum of Scrums. The Agile Release Train's agile teams will each have their own Scrum Master. The Scrum of Scrums, led by the Release Train Engineer, includes these scrum masters. The Release Train Engineer reports to the Product Owner during retrospective meetings. The RTE usually reports to the Agile Program Management office, which is part of the Lean Portfolio Management in SAFe (LPM).