While it is theoretically possible for a SAFe Agile Team to not use Scrum at all, I believe this scenario is unlikely in a SAFe implementation.
In SAFe, teams are recommended to use a combination of Scrum and XP. While the label for the combo admittedly looks unusual to me (ScrumXP) I don’t believe the combination of these approaches is in any way heretical: I have seen the two work very well with Scrum Teams myself.
Indeed, back in 2007, when I took some of my first steps in Scrum Teams as a Software Developer, I started with Scrum and XP together. Henrik Kniberg’s ‘Scrum and XP from the Trenches’ was a big influence.
Before that, Ken Schwaber and Mike Beedle, two of the biggest influences on the evolution of Scrum, wrote of how Scrum works with engineering practices. This quote was written in the same year as the Agile Manifesto and both men signed that document:
“If engineering practices are candy bars, then Scrum is a candy bar wrapper. That is to say that Scrum is superimposed and encapsulates whatever engineering practices already exist.”
(from ‘Agile Software Development with Scrum’, by Ken Schwaber and Mike Beedle, written in 2001)
In the most recent Scrum Guide, Ken Schwaber and Jeff Sutherland say that Scrum:
“functions well as a container for other techniques, methodologies, and practices.” (Scrum Guide)
To come back to the point: Scrum is a great container for other practices, but Scrum knowledge is an a priori requirement.
The SAFe framework is built around the rhythms and events of Scrum. A Program Increment (PI) is a series of Sprints — 5 Sprints in my context. The ‘PI Planning’ event happens at the beginning of the PI and is comparable to large-scale Sprint Planning. The ‘Inspect and Adapt’ event happens at the end of the PI and is comparable to a large scale Retrospective.
Even the idea of an Agile Release Train (ART) is comparable to the idea of a cross-functional team in Scrum, only operating at a higher scale. An ART is a team of teams, organised around a Value Stream. To help the ART deliver more value more effectively, dependencies between teams are systematically addressed: Scrum Masters are up to their necks in this activity, but more on this later.
Meanwhile, at the team level, a fundamental starting point for a SAFe Scrum Master is knowledge of the Scrum Events. A key difference is that SAFe refers to Sprints as Iterations: otherwise the events themselves look very familiar. Iteration Planning, Iteration Review, Iteration Retrospective, Daily Stand-Up.
I would only recommend consideration of a SAFe Scrum Master role if you are already very familiar with Scrum and how it is implemented by teams. SAFe will build on that.