That scene just uses lightmaps, has no realtime lights. Wasn't meant to be released in the first place, was just an internal demo to show a possible approach to reflection probe usage.
Currently there is no easy way to get PBR rendering in AppGameKit, you will have to dig in and do it yourself.
Unfortunately PBR is not something we can just throw onto a scene by applying a shader. The important part is generating and managing all the lighting data and reworking the render chain so that it can handle the necessary precision and ranges.
The engine would essentially need a full scene editor to make easy to use inbuilt PBR feasible or would have to move to a much higher minimum spec in order to use non-precalced realtime solutions.
On the upside, it's pretty fun to figure out how to to these things and you can optimize them for the exact needs of your project. But it is a lot of work for sure.