They announced it deeply hidden in some Insider build notes in February, but omitted any mentions in the release apparently. Here is the original notice from the Insider build:
Plugging in to use a Windows Mixed Reality headset will not work starting with this build. Windows Mixed Reality is no longer available to users as Windows Mixed Reality has been announced as deprecated. This includes the Mixed Reality Portal app, and Windows Mixed Reality for SteamVR and Steam VR Beta. Existing Windows Mixed Reality devices will continue to work with Steam through November 2026, if users remain on their current released version of Windows 11 (version 23H2) and do not upgrade to this year’s annual feature update for Windows 11 (version 24H2). This deprecation does not impact HoloLens.
As 24H2 is currently being rolled out, be careful if you are using WMR devices, like the G2 and others.
O7,

Plugging in to use a Windows Mixed Reality headset will not work starting with this build. Windows Mixed Reality is no longer available to users as Windows Mixed Reality has been announced as deprecated. This includes the Mixed Reality Portal app, and Windows Mixed Reality for SteamVR and Steam VR Beta. Existing Windows Mixed Reality devices will continue to work with Steam through November 2026, if users remain on their current released version of Windows 11 (version 23H2) and do not upgrade to this year’s annual feature update for Windows 11 (version 24H2). This deprecation does not impact HoloLens.
As 24H2 is currently being rolled out, be careful if you are using WMR devices, like the G2 and others.
O7,
