I found the solution for those of you still not finding tracking.
On the construction script of the BP_MotionController in the STEAMVR PLUGIN folder (ie not the VR template), you’ll see that this plugin uses a DEPRECATED node “Set Hand” enumerator
In the official UE4 Template, this has been updated to “Motion Source” instead, and if you don’t have SteamVR plugin installed, the Left/Right works perfectly.
With SteamVR Plugin installed, the “Motion Source” list does not include “Left” or “Right” and none of the other values seem to track.
With SteamVR Plugin installed, go back to your VR Template BP_MotionController Construction script and change the “Motion Source” back to deprecated “Set Hand” enumerator.
Presto!
Hopefully you guys can fix this up to work right once Epic fully deprecates the Hand enum currently working in the plugin.