I had a look at VR support for Urho3D and it's pretty experimental.
So I understand completely that it is not on your roadmap.
What a coincidence, I discovered RTA just this weekend !
It's awesome, open source, and made in Unity (which I use daily).
Just the thing to scratch my VR-fractal exploration itch :D
Didn't know there was beta access for Coral, going to check if it's still alive.