UE4 is still using an older version of ARCore. It would be good to know when they plan to update to the latest version.
For the meantime, you can compile the latest version from Google’s fork. Check out this thread for more information related to using the passthrough camera: Dynamic shadows · Issue #49 · google-ar/arcore-unreal-sdk · GitHub
Google are aware of issues with the colour space of the passthrough camera being wrong in certain shading modes - though it’s supposed to be fixed in the latest version - yet to try that out.