We're making Windows builds targeting Proton, and we're trying to find a way to tell if the device is running standalone (vs streamed/running on a desktop) so we can ensure graphics settings are put at a default that makes sense for a standalone device.
We're currently exploring using Steamworks.Net's IsSteamRunningOnSteamDeck() as a workaround, but given the new upcoming hardware it'd be nice to have a VR specific call for this.
I'm unaware of any other way to accomplish this functionality currently, through the OpenXR utils or through OpenVR.