Wayland's Weston Will Now Respect Your VR HMD
As was the case too with the X.Org Server up until some months back, Wayland's Weston compositor currently would try to take over VR HMDs like the HTC Vive as just another monitor output... But thanks to the work led by Keith Packard under contract for Valve to improve the X.Org and DRM components for better SteamVR handling on Linux, there is now the non-desktop bit plumbed through the Linux kernel's DRM infrastructure so VR HMDs will be treated as non-desktop display outputs. So user-space finally can know if a display output isn't intended as just another desktop display but for a special use-case like virtual reality.
With the latest Weston code, the compositor is making use of the non-desktop flag and no longer enabling these display outputs by default. But should you want to try mapping your VR HMD to part of your Weston desktop, that can still be done explicitly via the display configurable tunables in the weston.ini.
Overall though using the X.Org Server still is the preferred route for the time being if engaging in SteamVR gaming on Linux due to the better support, not to mention better NVIDIA driver compatibility. One other experimental alternative to that would be the Arcan display server with its VR desktop that does continue to be developed.