Question: How can I most easily export a Blender 2.8 scene to a Vive VR device? (I'm not talking about using Blender *while* wearing a headset; I mean just exporting a scene to be handed-off to a different PC with a headset.)

Answer: 
There exists a work in progress plugin thats claims to be able to view blend files in VR: <https://www.youtube.com/watch?v=9qAC8FTrU5s>

The HTC Vive Virtual Reality Headset is basically a Display. It has no software to show things by itself. So equally to your computer screen it can't open Files. 

First option would bee to find some software that is able to display 3D objects on your VR-Headset. You can import .obj/.mtl files to tiltrbush with some fiddling - maybe something more general exists. And after that you need to figure out the details how to export to that specific software.

Option two would be to create software that can render to your VR-Headset. That is easiest done with a Game engine like godotengine (open source), Unity3d or Unreal (proprietary with free entry level licenses).
I Would personally recommend Unity3d as it is beginner friendly and has nice Blender integration.
Making things look god in a game engine is some one topic of study though.
step1: download [UnrealEngine4](https://www.unrealengine.com/en-US/) from epic

step2: export fbx. (could have a bit of a learning curve depending on complexity and you'll likely have to scale on import)

step3: start a new vr project and load the motioncontrollermap.

step4: import to unreal (if you can't see it it could be really large or really small)

step5: drag on to scene 

step6: hit play and you can teleport around the scene. 

notes:
 if uvmapping is not correct go into the materials. add the texcoord node. set the index to the appropriate uv index.

if lighting is weird open the model in unreal. there are build settings under the details tab. here there is a generate lightmap checkbox you may not need this. under general settings there is lightmap coordinate index you may need to change this if you unchecked generate lightmap