Can a Project Manager with no technical expertise be a successful RTE?
Absolutely. The RTE is not a technical lead role, and project managers have many of the requisite skills that are important for being a good RTE. This role is about facilitation, coordination, and following sound processes for healthy Agile teams and trains.
You can read more about the role in our RTE article.
Do a Project Manager take a Leading SAFe course? Definitely.