The Linux DMA-BUF protocol for Wayland is widely used these days and supported by multiple compositors for negotiating optimal buffer allocation parameters between clients and compositors. The current fifth version of linux-dmabuf was marked as stable with it working out well and no need for any other changes before removing the “experimental” tag.
The new transient seat protocol for Wayland is for creating short-lived seats for remote users. These transient seats will be automatically removed as soon as the client disconnects. The transient seat protocol is intended for use with Wayland’s virtual input and virtual pointer protocols for remote desktop use.
Don’t SteamVR tools work on linux as well? Not that it’d help in your situation, where you’re stuck with proprietary GPU drivers and proprietary VR tools.